A: Nicol Bolas is the mysterious planeswalker who originally shattered Alara, using it's destruction to gain immense power. He disappears off into the Blind Eternities and gets up to all sorts of mischief (some of which we've seen in earlier sets/stories).
B: The events and aftershocks of Time Spiral leaves him weakened (at 'neo-walker' power level?)
C: He remembers Alara as his original power-source and sets off to investigate. Discovers the scattered shards, full of mana, but incomplete, unbalanced, nowhere near as powerful as the original plane of Alara.
D: With his long history of manipulations from behind the scenes, even in his weakened state he sets in motion plans to re-unite the shards (or takes advantage of a natural 'Conflux' that is bringing them back together).
E: Once restored, Alara can again be drained to power his ascension back to godhood. Unless someone stops him of course...
F: Pawns/Allies on each shard:
Grixis: Malfegor? (Demon/Dragon spawn of Nicol Bolas?)
Jund: Sarkhan Vol? Viashino? (They have a history of serving dragons.)
Bant: Order of the Skyward Eye? (Awaiting his return?) Skyward Eye Prophets/Dragonsoul Knight (openly worshipping him?)
Esper: Vectis? Ethersworn? Tezzeret? (Is Nicol Bolas the true source of Etherium and is it essential for his plans to reunite the shards?)
Naya: Minotaurs?? Ajani? (Is he manipulating his thirst for vengeance?)
One problem I see with the 'Call' mechanic is a memory issue. If you don't have the Planeswalker card in your hand and it is buried somewhere in your library, then you are relying on your memory of the Call conditions as to when you can activate the Call.
Let's look at the broad idea of a planeswalker:
Players = Planeswalkers. This has been a part of Magic's history since the beginning, but even if it has been changed, all that does is this:
Players < Planeswalkers.
So we are looking at a single card that is more powerful than the person playing it?
If we take the first case, then playing a Planeswalker should have a power level in a duel similar to having a friend sit down next to you with his deck and start playing simultaneously against your opponent. That's a card way beyond broken which is obviously why Wizards have never attempted to represent Planeswalkers on cardboard - until now?
Even a 'vanilla' Planeswalker would look something like:
D.X. Machina
Planeswalker
You gain 20 life and draw 7 cards. Your maximum handsize is 14. You may play one extra turn immediately after your opponent's turn and before your own.
From a flavour perspective, Planeswalkers will have to be more Legendary than legends, and if they have a P/T it would have to be Infinity/Infinity. Others have already pointed out how sad it would be to have Urza or Serra as simple 'hired guns' fighting for you in the red zone which argues against them following the Creature template and being directly involved in combat.
Planeswalkers can step from on world to another in the blink of an eye. This hardly seems like the behaviour of your average permanent but they are much more than just an ephemeral spell. They are so powerful that it seems almost sacrilegious to have them fall to simple 'creature removal' or even bounce which would suggest either immunity to spells (indestructibility and untargetable?) which would eat up a fair amount of text box room leaving little left for flavour which has to dominate a Planeswalker card, or that they exist in a zone (RFG?) that makes them relatively untouchable.
Also remember the recent article about the 'Grandeur' mechanic which is an attempt to make Legends cooler to collect and have multiple copies of. It would seem strange then to reverse that policy and introduce a new type of card that you can only play one of in a deck.
The new Lhurgoyf suggests that Planeswalkers will start in your library just like any other card (as I can't imagine any other way they would end up in your graveyard), and again it goes against the grain to think that just ponying up some mana (even large amounts of mana) can bind a Planeswalker to your will. The ideas of Dr Pops and others of an alliance born from situations that might intrigue a Planeswalker definitely have merit.
Planeswalkers twist the rules of time and space - where better to meet our first Planeswalker than in the Time Spiral block where those rules have been shattered? Planeswalkers begin as mere mortals who contain a spark that when 'ignited' (usually by a traumatic death and often producing catastrophic results for the surrounding area) elevates them to near godhood.
What if Planeswalkers interact with time itself?
Past (Graveyard)
Present (In Play)
Future (Hand)
Eternity (RFG?)
What if Planeswalkers have abilities that activate when they exist in a particular zone? In that way they are 'immortal' in that you can reveal a Planeswalker in your hand for one effect. Play him for another. Sacrifice him for a third. All your opponent can do is move him around. If he hits you with discard or destroys the Planeswalker, the graveyard ability activates. If he bounces your Planeswalker, the in hand ability is accessible.
Finally, an extremely rare trigger (perhaps having a copy of the card in all three zones - hand, play, graveyard plus a specific situation that suits the PW's flavour) will trigger 'Ascension' (that destroys all your other permanents?) putting a copy of the card in the RFG zone with a 'Spark' counter which activates it's ultimate ability (or perhaps just all of it's abilities simultaneously?)
Urza (No casting cost)
Planeswalker
Urza is blue.
During your upkeep if you control more than 7 artifacts you may put Urza into play from your hand or the graveyard.
All your spells gain affinity for artifacts.
If Urza is in your graveyard, all artifacts you control are indestructible.
Channel -- 4U, discard Urza from your hand: Put target artifact from any graveyard into play under your control.
Ascension -- Remove from the game cards named Urza from your hand and graveyard, sacrifice all non-artifact permanents: All artifacts you control gain "T: Deal X damage to target creature or player where X is the number of artifacts in play."
Of course that isn't balanced and probably wouldn't fit on a card, but it gives an idea of the 'WOW' factor a planeswalker would need, I think, even though it is far too wordy and cluttered.
Yawgmoth (No casting cost)
Planeswalker
Yawgmoth is black.
During your upkeep if you have 7 or more creatures in your graveyard you may put Yawgmoth into play from your hand.
All creatures you control gain deathtouch.
If Yawgmoth is in your graveyard, all creatures you control are black and gain "B: Regenerate this creature."
Forecast -- 2BB, sacrifice a creature, reveal Yawgmoth from your hand: Destroy target creature, it can't be regenerated. Its controller loses life equal to its power, you gain life equal to its toughness.
Ascension -- Remove from the game cards named Yawgmoth from your hand and graveyard, sacrifice Yawgmoth and all non-black permanents. Opponents lose X life where X is the number of permanents you control. They may sacrifice X permanents to prevent this loss of life.
Another idea I had for Planeswalkers' abilities might be that they are very powerful mana sources as they are usually depicted as having access to huge amounts of mana. Perhaps a Planeswalker could 'supercharge' existing mana sources (especially ones that match their colour(s))?
Despite my attempts to create worthy Planeswalkers, I believe a true Planeswalker card will be iconic, powerful and above all, elegant - which my ideas are not at this stage!
Here's my take on why Tribal is a type and not a supertype. It's a bit arcane and is based on my limited understanding of the rules, so it might be completely wrong.
From what I understand, supertypes mostly appear on permanents and are inclusive in that they give a common set of properties to a range of cards, independent of their types or sub-types that can then be used as hooks for mechanics.
For example, a Snow Land that then has it's type changed to Creature would still be Snow. Each layer of types operates independently of each other.
From the limited sample set we have so far, the function of Tribal seems to be what I would call an 'anti-type'. It acts as a reminder to players that even though a permanent bears familiar creature sub-types (such as Rebel, Sliver, etc.) that does NOT make it a creature. Unless a card explicitly has 'Creature' on it's type line (or another card puts it there) then a Tribal card is not a creature and should be treated accordingly. In effect it is broadening the creature sub-types and their interactions by giving them a new card type that they can apply to.
This seems to be supported by variations in the rules text of FS slivers:
Virulent Sliver: All Sliver creatures have poisonous 1.
Sliver Legion: All Sliver creatures get +1/+1 for each other Sliver in play.
Homing Sliver: Each Sliver card in each player's hand has Slivercycling
Mesmeric Sliver: All Slivers have "When this permanent comes into play fateseal 1".
They suggest we will see Sliver cards that are not creatures either in FS or the near future.
Now we come to the reason why Tribal probably is not a supertype. If it was then it seems to me it would 'over-rule' any change of type thus making many type-changing spells (such as land-animation) redundant, or more confusing to use on Tribal cards.
Tribal seems to operate under exclusion: "this card is NOT a creature unless you are told otherwise by its type." As all this interaction takes place in the 'type' layer it makes sense for Tribal to exist solely within that layer.
Unlike supertypes which operate under inclusion: "this card is Snow (or Legendary) regardless of its type". There is no direct interaction between the supertype and type beyond the fact that some supertypes are associated with particular types.
I don't think it is a coincidence that we recently had an article highlighting the work of the 'rules gurus' at the same time as FS Previews because the introduction of so many new and combined keywords will obviously push the rules to the limits of comprehensibility. Anything that simplifies rule interactions (as I believe the 'Tribal' type does) was probably grabbed with much relief in R&D.
Here is an alternative (and simpler) way to look at it:
Supertype
Type
Sub-type
These operate in a hierarchy that is mostly linear so that there is no direct interaction between Supertypes and Sub-types. Currently Creature sub-types interact exclusively with the Creature Type. As Tribal is all about broadening the interaction of creature sub-types (Rebel, Sliver, etc.) then it has to operate in the Type layer to also interact with these sub-types. Making Tribal a Supertype would require an extra layer of rules needed to link it back to the creature sub-types.
I tossed a few Izzet-themed guesses into the Orb and here's what came up:
spire - 1 (I guessed Niv-Mizzet likes a place to roost with a good view)
mirrors - 1 (If we are talking copying spells or re-directing spells this seemed appropriate)
smoke - 1 (Niv-Mizzet is a dragon and the Izzet are mad scientists so there's bound to be smoke and explosions and so forth.)
firemind - 6 (So far I can only account for 4 of these, unless the two more are in flavour text somewhere, maybe the 'guildhall' mentions the Firemind as well)
So how about this:
Whozzit, Spire of Smoke and Mirrors
In reality, if 'smoke' and 'mirrors' do go together it is on some Izzet enchantment or sorcery. But I think the spire is a good bet for the Izzet land.
So maybe:
Whozzit, Spire of the Firemind
Or I could be wrong and it might just be the relatively boring 'Izzet Spire' guildland.
Moving on to the mechanic - what do we know about the Izzet so far:
Replicate - they can copy some of their spells
Guildmage - more spell copying
Gigadrowse - tap permanent
Siege of Towers - animate mountains
Stitch in Time - flip a coin, take another turn
Niv-Mizzet - draw a card, ping something
Invoke the Firemind - Draw X or Burn X
Mimeofacture - Steal copy of permanent from opponent's library
That is a fairly wide range of some pretty crazy effects - very Izzet indeed!
So what can the land do to support this?
Simply more spell copying or more card draw seems redundant and a little predictable. Selesnya's land simply pumped out more tokens - again that is very Selesnya, but a land that just does more of the same doesn't strike me as very Izzet.
Spell re-direction looks very possible, and the draw/discard option seems likely too. So I'll put something a little more radical on the table.
Let's look at the other side of the equation: with all this replicating and hands full of cards what will an Izzet Mage need more than anything? Mana. So maybe the Spire gives some kind of mana acceleration?
" ?UR, T : Until end of turn you may sacrifice any lands you control and add UR to your mana pool for each land sacrificed in this way."
There probably won't be racial tribes, but there could be occupation tribes. Ravnica is really just 10 occupation unions fighting all the time.
Soldiers there, barbarians here, shamen and warriors up there, a couple of wizards gulds, some zombies, a rogue network, a bunh of clerics, and mercenaries someplace.
The occupations are very much like the racial types. No guild is that specialised. They all have fighters, healers, wizards and so forth. The combat focus of Magic means we mostly see these on the cards anyway. Background material such as the novels suggest a much deeper organisational structure in most of the guilds.
The Boros are much more than just the 'army' guild, with subgroups such as the League of Wojek which do the street-level policing for example.
Here are some examples of common occupation types that are spread through the guilds:
Cleric - Selesnya and Boros, almost certainly Orzhov and possibly Azorius
Soldier - Selesnya and Boros, possibly Azorius
Zombie - Dimir and Golgari, probably Orzhov and possibly Rakdos
Izzet Shockland
-Seeing lots of translations for this thing...
For what concerns me, the second word in the name could be "Vapori" (Vapors). The first word is unreadable, but in the text of the card it seems "Fucine" (Forges). For sure it's plural, as long as the article is "le" which is female-plural. So it could be "Forges of Vapor(s)", except that the name would suck :-(
An alternative translation for 'Vapore' is steam and that is my personally preferred one.
The translation of 'Steam Furnace' in Babelfish is 'Fornace del Vapore' which seems to fit quite well, both in length and in feel for the industrial artwork and the Izzet mindset.
The colour-paired guild structure fights against the concept of tribalism in my opinion, because most races and many classes (with the exception of humans) are restricted to one or two colours. In traditional Magic that limits their placement but in the city of Ravnica they are spoiled for choice.
For example: Goblins - traditional chaotic Red race. In old-school Magic they live in the Mountains and cause trouble. Now we move to Ravnica and it's a whole new ball game. The Mountains have become Towers and Goblins have four Red Guilds to choose from. The brainy/curious Goblin tinkerers can sign up with Niv-Mizzet and blow stuff up in his laboratories. The crazy/violent Goblin beserkers can join the Rakdos cult and labour in the mines. The anarchist/warrior Goblins can run away and join the Gruul out in what's left of the wilderness. Finally the honourable/ambitious Goblins can go see the Boros recruiters and go to bootcamp at Sunhome. That's just one race and one colour.
All the cosmopolitan opportunities that a big city like Ravnica offers splinters the traditional 'racial' models that exist in more traditional Magic worlds where social systems are usually tribal or medieval at best. Ravnica is an urbanised culture and it is a refreshing change of pace from more leisurely and more primitive fantasy worlds.
I'm a little concerned by the memory issues of the RFG/imprint ideas, as it will get very complicated once you have multiple hauntings going on, and if this is the guild keyword then you probably will if you are playing Orzhov. The alternative is to somehow 'attach' haunting cards to their targets but that presents its own problems.
Let's take a step back and consider something simpler: both B & W have recursion in common, so let's stick haunt cards in the graveyard as normal. You have to admit that cards sitting in the graveyard with a keyword called 'haunt' seems appropriate. Also look at the card itself. We have a cheap cost and a 'meh' effect. It almost demands that you cast it and get it into the graveyard - it isn't that exciting in your hand!
Let's also assume that 'haunt' is an action rather than a state. A haunt card doesn't hang around in limbo for turn after turn, instead it sits quietly in the graveyard until YOU choose to activate it.
What if a haunting literally scares its target to death? Then the original card we've seen makes a bit more sense:
Black Card we don't know name of -
Sorcery
Target player discards a card.
Haunt
When the creature, "Black Card we don't know name of" haunts is put into a graveyard, target player discards a card.
It's that "When the creature..." bit that gets me, it seems to say that the haunted creature is DEFINITELY going to the graveyard. Why not say "If" if the haunting card is just waiting around until something kills it? So let's say that the haunting itself kills the target:
Haunt ([Additional cost?], sacrifice target creature you control: Return ~ from the graveyard to your hand.)
If it works like this then you could pay BB and sacrifice a creature and your opponent discards three cards. Is it looking healthier now?
Arguments for: Both B & W are willing to sacrifice creatures to gain something. It certainly matches the 'Guild of Deals' ethos of trading lives for power and doing dark deals. Dimir's milling tricks give the Orzhov more options, not less. Synergises with Golgari dredge cards. The spirit tokens could power white convoke spells. Haunt works on any kind of card, creature or spell.
Arguments against: Is this too similar to Dredge? Is sacrifice too harsh for the Orzhov? We are all assuming that Rakdos will be the sacrifice-addicts. Unless the haunting balances itself? How about this alternative:
Haunt ([Additional cost?], sacrifice target creature you control: Return ~ from the graveyard to your hand, and put a 1/1 black spirit creature token with flying into play.)
That seems more like a deal the Orzhov could live with and the spirit token ties in nicely with the haunting theme. The spirits could match the colour of the spell that creates them: B, W or B/W.
My take on Flight of Fancy is that it definitely has an Izzet twist. It is a blue spell but the artwork shows a goblin (a red creature). Goblins are explicitly associated with the Izzet in the Ravnica novel. Also the flavour text talks about inspiration - another Izzet trait. Finally the draw mechanic matches with Izzet's desire for new info.
Good call on Fiery Conclusion. I think it was mainly space reasons that caused the Gruul to be left out - although possibly it was because their view of that sacrifice would have been somwhere between Boros and Rakdos and was too difficult to differentiate from them. My suggestion for the Gruul viewpoint would be: "The Gruul warrior saw a blaze of glory."
Good call with Trophy Hunter - she looks quite feral and very Gruul.
"Growing angry". Seems pretty self-explanatory - when people get angry they fight - Gruul War-Clans live to fight, and combat makes them stronger (think Klingons for a cultural reference).
Green's pack mentality binds Red's aggressiveness into a culture that thrives on violence. Gruul members prove their status through trials of combat and never refuse a challenge (which leaves them vulnerable to tricky folks who don't play by the rules - see Dimir, Orzhov, etc).
The Gruul will hate evasion but trample fits in well (it doesn't matter who gets in their way, they're still going to hurt you). Doublestrike ties into their combat prowess. +1/+1 counters tied to combat damage (perhaps even damage received?) sound pretty Gruul - the proud scars of battle.
It's no surprise that their leader is a giant cyclops with a big axe!
In the case of Quickchange, I suppose someone has already pointed out that the coloured auras all seem to be guild-oriented.
Green/Gorgon - Golgari
Blue/Skeletal - Dimir
Black/White - Orzhov (you can just make out the sun symbol on the figure's tunic)
White/Dryad - Selesnya
Red/Mage - Boros? Perhaps Izzet? The design seems very Borosian but haven't found an existing card that closely matches it yet.
The quickchange theme would probably fit best with the Simic I think. Azorius are all about enforcing the rules, not breaking them.
I think we should also consider that in the name of synergy, these mono-colour 'freelancers' will almost certainly work with several guilds that share their colour. We know that the Guilds are the dominant social, economic and political powers of the city but that the majority of the citizens are guildless.
Putting it into flavour terms, a Red citizen will have to be able to deal with the Izzet, Gruul, Rakdos and Boros just to make it through the day.
In fact Quickchange says so, right in its flavour text.
A: Nicol Bolas is the mysterious planeswalker who originally shattered Alara, using it's destruction to gain immense power. He disappears off into the Blind Eternities and gets up to all sorts of mischief (some of which we've seen in earlier sets/stories).
B: The events and aftershocks of Time Spiral leaves him weakened (at 'neo-walker' power level?)
C: He remembers Alara as his original power-source and sets off to investigate. Discovers the scattered shards, full of mana, but incomplete, unbalanced, nowhere near as powerful as the original plane of Alara.
D: With his long history of manipulations from behind the scenes, even in his weakened state he sets in motion plans to re-unite the shards (or takes advantage of a natural 'Conflux' that is bringing them back together).
E: Once restored, Alara can again be drained to power his ascension back to godhood. Unless someone stops him of course...
F: Pawns/Allies on each shard:
Grixis: Malfegor? (Demon/Dragon spawn of Nicol Bolas?)
Jund: Sarkhan Vol? Viashino? (They have a history of serving dragons.)
Bant: Order of the Skyward Eye? (Awaiting his return?) Skyward Eye Prophets/Dragonsoul Knight (openly worshipping him?)
Esper: Vectis? Ethersworn? Tezzeret? (Is Nicol Bolas the true source of Etherium and is it essential for his plans to reunite the shards?)
Naya: Minotaurs?? Ajani? (Is he manipulating his thirst for vengeance?)
Let's look at the broad idea of a planeswalker:
Players = Planeswalkers. This has been a part of Magic's history since the beginning, but even if it has been changed, all that does is this:
Players < Planeswalkers.
So we are looking at a single card that is more powerful than the person playing it?
If we take the first case, then playing a Planeswalker should have a power level in a duel similar to having a friend sit down next to you with his deck and start playing simultaneously against your opponent. That's a card way beyond broken which is obviously why Wizards have never attempted to represent Planeswalkers on cardboard - until now?
Even a 'vanilla' Planeswalker would look something like:
D.X. Machina
Planeswalker
You gain 20 life and draw 7 cards. Your maximum handsize is 14. You may play one extra turn immediately after your opponent's turn and before your own.
From a flavour perspective, Planeswalkers will have to be more Legendary than legends, and if they have a P/T it would have to be Infinity/Infinity. Others have already pointed out how sad it would be to have Urza or Serra as simple 'hired guns' fighting for you in the red zone which argues against them following the Creature template and being directly involved in combat.
Planeswalkers can step from on world to another in the blink of an eye. This hardly seems like the behaviour of your average permanent but they are much more than just an ephemeral spell. They are so powerful that it seems almost sacrilegious to have them fall to simple 'creature removal' or even bounce which would suggest either immunity to spells (indestructibility and untargetable?) which would eat up a fair amount of text box room leaving little left for flavour which has to dominate a Planeswalker card, or that they exist in a zone (RFG?) that makes them relatively untouchable.
Also remember the recent article about the 'Grandeur' mechanic which is an attempt to make Legends cooler to collect and have multiple copies of. It would seem strange then to reverse that policy and introduce a new type of card that you can only play one of in a deck.
The new Lhurgoyf suggests that Planeswalkers will start in your library just like any other card (as I can't imagine any other way they would end up in your graveyard), and again it goes against the grain to think that just ponying up some mana (even large amounts of mana) can bind a Planeswalker to your will. The ideas of Dr Pops and others of an alliance born from situations that might intrigue a Planeswalker definitely have merit.
Planeswalkers twist the rules of time and space - where better to meet our first Planeswalker than in the Time Spiral block where those rules have been shattered? Planeswalkers begin as mere mortals who contain a spark that when 'ignited' (usually by a traumatic death and often producing catastrophic results for the surrounding area) elevates them to near godhood.
What if Planeswalkers interact with time itself?
Past (Graveyard)
Present (In Play)
Future (Hand)
Eternity (RFG?)
What if Planeswalkers have abilities that activate when they exist in a particular zone? In that way they are 'immortal' in that you can reveal a Planeswalker in your hand for one effect. Play him for another. Sacrifice him for a third. All your opponent can do is move him around. If he hits you with discard or destroys the Planeswalker, the graveyard ability activates. If he bounces your Planeswalker, the in hand ability is accessible.
Finally, an extremely rare trigger (perhaps having a copy of the card in all three zones - hand, play, graveyard plus a specific situation that suits the PW's flavour) will trigger 'Ascension' (that destroys all your other permanents?) putting a copy of the card in the RFG zone with a 'Spark' counter which activates it's ultimate ability (or perhaps just all of it's abilities simultaneously?)
Urza (No casting cost)
Planeswalker
Urza is blue.
During your upkeep if you control more than 7 artifacts you may put Urza into play from your hand or the graveyard.
All your spells gain affinity for artifacts.
If Urza is in your graveyard, all artifacts you control are indestructible.
Channel -- 4U, discard Urza from your hand: Put target artifact from any graveyard into play under your control.
Ascension -- Remove from the game cards named Urza from your hand and graveyard, sacrifice all non-artifact permanents: All artifacts you control gain "T: Deal X damage to target creature or player where X is the number of artifacts in play."
Of course that isn't balanced and probably wouldn't fit on a card, but it gives an idea of the 'WOW' factor a planeswalker would need, I think, even though it is far too wordy and cluttered.
Yawgmoth (No casting cost)
Planeswalker
Yawgmoth is black.
During your upkeep if you have 7 or more creatures in your graveyard you may put Yawgmoth into play from your hand.
All creatures you control gain deathtouch.
If Yawgmoth is in your graveyard, all creatures you control are black and gain "B: Regenerate this creature."
Forecast -- 2BB, sacrifice a creature, reveal Yawgmoth from your hand: Destroy target creature, it can't be regenerated. Its controller loses life equal to its power, you gain life equal to its toughness.
Ascension -- Remove from the game cards named Yawgmoth from your hand and graveyard, sacrifice Yawgmoth and all non-black permanents. Opponents lose X life where X is the number of permanents you control. They may sacrifice X permanents to prevent this loss of life.
Another idea I had for Planeswalkers' abilities might be that they are very powerful mana sources as they are usually depicted as having access to huge amounts of mana. Perhaps a Planeswalker could 'supercharge' existing mana sources (especially ones that match their colour(s))?
Despite my attempts to create worthy Planeswalkers, I believe a true Planeswalker card will be iconic, powerful and above all, elegant - which my ideas are not at this stage!
From what I understand, supertypes mostly appear on permanents and are inclusive in that they give a common set of properties to a range of cards, independent of their types or sub-types that can then be used as hooks for mechanics.
For example, a Snow Land that then has it's type changed to Creature would still be Snow. Each layer of types operates independently of each other.
From the limited sample set we have so far, the function of Tribal seems to be what I would call an 'anti-type'. It acts as a reminder to players that even though a permanent bears familiar creature sub-types (such as Rebel, Sliver, etc.) that does NOT make it a creature. Unless a card explicitly has 'Creature' on it's type line (or another card puts it there) then a Tribal card is not a creature and should be treated accordingly. In effect it is broadening the creature sub-types and their interactions by giving them a new card type that they can apply to.
This seems to be supported by variations in the rules text of FS slivers:
Virulent Sliver: All Sliver creatures have poisonous 1.
Sliver Legion: All Sliver creatures get +1/+1 for each other Sliver in play.
Homing Sliver: Each Sliver card in each player's hand has Slivercycling
Mesmeric Sliver: All Slivers have "When this permanent comes into play fateseal 1".
They suggest we will see Sliver cards that are not creatures either in FS or the near future.
Now we come to the reason why Tribal probably is not a supertype. If it was then it seems to me it would 'over-rule' any change of type thus making many type-changing spells (such as land-animation) redundant, or more confusing to use on Tribal cards.
Tribal seems to operate under exclusion: "this card is NOT a creature unless you are told otherwise by its type." As all this interaction takes place in the 'type' layer it makes sense for Tribal to exist solely within that layer.
Unlike supertypes which operate under inclusion: "this card is Snow (or Legendary) regardless of its type". There is no direct interaction between the supertype and type beyond the fact that some supertypes are associated with particular types.
I don't think it is a coincidence that we recently had an article highlighting the work of the 'rules gurus' at the same time as FS Previews because the introduction of so many new and combined keywords will obviously push the rules to the limits of comprehensibility. Anything that simplifies rule interactions (as I believe the 'Tribal' type does) was probably grabbed with much relief in R&D.
Here is an alternative (and simpler) way to look at it:
Supertype
Type
Sub-type
These operate in a hierarchy that is mostly linear so that there is no direct interaction between Supertypes and Sub-types. Currently Creature sub-types interact exclusively with the Creature Type. As Tribal is all about broadening the interaction of creature sub-types (Rebel, Sliver, etc.) then it has to operate in the Type layer to also interact with these sub-types. Making Tribal a Supertype would require an extra layer of rules needed to link it back to the creature sub-types.
The 'red chaos knight' we've seen in artwork seems to be ankle deep in blood (well his mount is anyway) rather than sulfur.
The Silver Knight/Sulfur Knight resonance is nice, but wouldn't Black Knight/Blood Knight work just as well?
spire - 1 (I guessed Niv-Mizzet likes a place to roost with a good view)
mirrors - 1 (If we are talking copying spells or re-directing spells this seemed appropriate)
smoke - 1 (Niv-Mizzet is a dragon and the Izzet are mad scientists so there's bound to be smoke and explosions and so forth.)
firemind - 6 (So far I can only account for 4 of these, unless the two more are in flavour text somewhere, maybe the 'guildhall' mentions the Firemind as well)
So how about this:
Whozzit, Spire of Smoke and Mirrors
In reality, if 'smoke' and 'mirrors' do go together it is on some Izzet enchantment or sorcery. But I think the spire is a good bet for the Izzet land.
So maybe:
Whozzit, Spire of the Firemind
Or I could be wrong and it might just be the relatively boring 'Izzet Spire' guildland.
Moving on to the mechanic - what do we know about the Izzet so far:
Replicate - they can copy some of their spells
Guildmage - more spell copying
Gigadrowse - tap permanent
Siege of Towers - animate mountains
Stitch in Time - flip a coin, take another turn
Niv-Mizzet - draw a card, ping something
Invoke the Firemind - Draw X or Burn X
Mimeofacture - Steal copy of permanent from opponent's library
That is a fairly wide range of some pretty crazy effects - very Izzet indeed!
So what can the land do to support this?
Simply more spell copying or more card draw seems redundant and a little predictable. Selesnya's land simply pumped out more tokens - again that is very Selesnya, but a land that just does more of the same doesn't strike me as very Izzet.
Spell re-direction looks very possible, and the draw/discard option seems likely too. So I'll put something a little more radical on the table.
Let's look at the other side of the equation: with all this replicating and hands full of cards what will an Izzet Mage need more than anything? Mana. So maybe the Spire gives some kind of mana acceleration?
" ?UR, T : Until end of turn you may sacrifice any lands you control and add UR to your mana pool for each land sacrificed in this way."
The occupations are very much like the racial types. No guild is that specialised. They all have fighters, healers, wizards and so forth. The combat focus of Magic means we mostly see these on the cards anyway. Background material such as the novels suggest a much deeper organisational structure in most of the guilds.
The Boros are much more than just the 'army' guild, with subgroups such as the League of Wojek which do the street-level policing for example.
Here are some examples of common occupation types that are spread through the guilds:
Cleric - Selesnya and Boros, almost certainly Orzhov and possibly Azorius
Soldier - Selesnya and Boros, possibly Azorius
Zombie - Dimir and Golgari, probably Orzhov and possibly Rakdos
An alternative translation for 'Vapore' is steam and that is my personally preferred one.
I can't help pointing out this:
Old speculation post
The translation of 'Steam Furnace' in Babelfish is 'Fornace del Vapore' which seems to fit quite well, both in length and in feel for the industrial artwork and the Izzet mindset.
For example: Goblins - traditional chaotic Red race. In old-school Magic they live in the Mountains and cause trouble. Now we move to Ravnica and it's a whole new ball game. The Mountains have become Towers and Goblins have four Red Guilds to choose from. The brainy/curious Goblin tinkerers can sign up with Niv-Mizzet and blow stuff up in his laboratories. The crazy/violent Goblin beserkers can join the Rakdos cult and labour in the mines. The anarchist/warrior Goblins can run away and join the Gruul out in what's left of the wilderness. Finally the honourable/ambitious Goblins can go see the Boros recruiters and go to bootcamp at Sunhome. That's just one race and one colour.
All the cosmopolitan opportunities that a big city like Ravnica offers splinters the traditional 'racial' models that exist in more traditional Magic worlds where social systems are usually tribal or medieval at best. Ravnica is an urbanised culture and it is a refreshing change of pace from more leisurely and more primitive fantasy worlds.
Let's take a step back and consider something simpler: both B & W have recursion in common, so let's stick haunt cards in the graveyard as normal. You have to admit that cards sitting in the graveyard with a keyword called 'haunt' seems appropriate. Also look at the card itself. We have a cheap cost and a 'meh' effect. It almost demands that you cast it and get it into the graveyard - it isn't that exciting in your hand!
Let's also assume that 'haunt' is an action rather than a state. A haunt card doesn't hang around in limbo for turn after turn, instead it sits quietly in the graveyard until YOU choose to activate it.
What if a haunting literally scares its target to death? Then the original card we've seen makes a bit more sense:
It's that "When the creature..." bit that gets me, it seems to say that the haunted creature is DEFINITELY going to the graveyard. Why not say "If" if the haunting card is just waiting around until something kills it? So let's say that the haunting itself kills the target:
Haunt ([Additional cost?], sacrifice target creature you control: Return ~ from the graveyard to your hand.)
If it works like this then you could pay BB and sacrifice a creature and your opponent discards three cards. Is it looking healthier now?
Arguments for: Both B & W are willing to sacrifice creatures to gain something. It certainly matches the 'Guild of Deals' ethos of trading lives for power and doing dark deals. Dimir's milling tricks give the Orzhov more options, not less. Synergises with Golgari dredge cards. The spirit tokens could power white convoke spells. Haunt works on any kind of card, creature or spell.
Arguments against: Is this too similar to Dredge? Is sacrifice too harsh for the Orzhov? We are all assuming that Rakdos will be the sacrifice-addicts. Unless the haunting balances itself? How about this alternative:
Haunt ([Additional cost?], sacrifice target creature you control: Return ~ from the graveyard to your hand, and put a 1/1 black spirit creature token with flying into play.)
That seems more like a deal the Orzhov could live with and the spirit token ties in nicely with the haunting theme. The spirits could match the colour of the spell that creates them: B, W or B/W.
My take on Flight of Fancy is that it definitely has an Izzet twist. It is a blue spell but the artwork shows a goblin (a red creature). Goblins are explicitly associated with the Izzet in the Ravnica novel. Also the flavour text talks about inspiration - another Izzet trait. Finally the draw mechanic matches with Izzet's desire for new info.
Good call on Fiery Conclusion. I think it was mainly space reasons that caused the Gruul to be left out - although possibly it was because their view of that sacrifice would have been somwhere between Boros and Rakdos and was too difficult to differentiate from them. My suggestion for the Gruul viewpoint would be: "The Gruul warrior saw a blaze of glory."
"Growing angry". Seems pretty self-explanatory - when people get angry they fight - Gruul War-Clans live to fight, and combat makes them stronger (think Klingons for a cultural reference).
Green's pack mentality binds Red's aggressiveness into a culture that thrives on violence. Gruul members prove their status through trials of combat and never refuse a challenge (which leaves them vulnerable to tricky folks who don't play by the rules - see Dimir, Orzhov, etc).
The Gruul will hate evasion but trample fits in well (it doesn't matter who gets in their way, they're still going to hurt you). Doublestrike ties into their combat prowess. +1/+1 counters tied to combat damage (perhaps even damage received?) sound pretty Gruul - the proud scars of battle.
It's no surprise that their leader is a giant cyclops with a big axe!
The Azorius symbol could almost be a pictograph for bureaucracy: A complex maze surrounded by strong walls.
Rakdos just shouts death and destruction.
Finally the Simic is the one I actually find the creepiest. The most basic symbol of nature, the tree, twisted into something alien and disturbing.
Wonderful stuff all round.
Green/Gorgon - Golgari
Blue/Skeletal - Dimir
Black/White - Orzhov (you can just make out the sun symbol on the figure's tunic)
White/Dryad - Selesnya
Red/Mage - Boros? Perhaps Izzet? The design seems very Borosian but haven't found an existing card that closely matches it yet.
The quickchange theme would probably fit best with the Simic I think. Azorius are all about enforcing the rules, not breaking them.
Putting it into flavour terms, a Red citizen will have to be able to deal with the Izzet, Gruul, Rakdos and Boros just to make it through the day.
In fact Quickchange says so, right in its flavour text.