My R/B section was Daretti, K. Command, Grenzo, and Falkenrath, I recently switched it to Daretti, K. Command, Dreadbore, and Vial Smasher. Grenzo is a bit mana intensive and the ability while INCREDIBLY fun, whiffs with some regularity. Falkenrath is solid, but I wanted some 2CC PW removal and Vial Smasher doesn't ask that you do anything but cast spells over the game. On rare occasion the requirement that you cast the more expensive spell first to take full advantage of him might be a hindrance, but this is a minor quibble. Also, Vial Smasher with Fireblast is disgusting.
One feature of the guild mechanics in GRN are that they have some synergy with other abilities that share a color whether it is direct synergy like surveil and jump-start or indirect synergy like GW creating lots of creatures that can be mentored. With that in mind I'm going to create the five mechanics I would like to see from Ravnica Allegiance.
GU: Biomutate - When casting this creature you may return a creature you control to its owner's hand. If you do this enters the battlefield with +1/+1 counters equal to half of that creature's power rounded up.
RG: Overwhelm - If you control the creature with the greatest power, do X.
RB: Backlash - You may lose life equal to this card's converted mana cost when you cast this, if you do than do X
UW: Proscribe (X) - This permanent enters the battlefield with X law counters on it. At the beginning of your upkeep remove a law counter from it.
WB: Exsoul (Cost): You may exile this card from your graveyard. If you do create a 1/1 black and white spirit token with flying.
A few sample cards for fun. Absorbing OozeG
Creature - Ooze (U)
Biomutate - When you cast Absorbing Ooze you may return a creature you control to your hand, if you do Absorbing Ooze enters the battlefield with +1/+1 counters equal to half of that creature's power rounded up.
(0/0)
Whirlwind Lizard3UG
Creature - Mutant Lizard (R)
Flash
You may return an opponent's creature as though it were under your control if using Whirlwind Lizard's biomutate ability.
Biomutate - When you cast Whirlwind Lizard you may return a creature you control to your hand, if you do Whirlwind Lizard enters the battlefield with +1/+1 counters equal to half of that creature's power rounded up.
(2/2)
Gruul Grunt1R
Creature - Giant (U)
Overwhelm - If you control the creature with the greatest power during your end step, Gruul Grunt deals 1 damage to target creature an opponent controls.
(3/1)
SmashRG
Instant (R)
Target creature you control gets +2/+2 and trample until end of turn.
Overwhelm - If you control the creature with the greatest power you may have it deal damage equal to its power to target creature an opponent controls.
Blood Fencer1RB
Creature (U)
Double Strike
Backlash - You may pay 3 life when Blood Fencer enters the battlefield. If you do it enters the battlefield with a +1/+1 counter.
(1/1)
Demonic ParadeX
Sorcery (R)
Backlash
Create X 1/1 Black and Red demons with haste.
When you cast Demonic Parade, you may pay life equal to its converted mana cost. If you do, demons you control get +1/+1 until end of turn and gain "when this creature attacks it deals 1 damage to defending player" until end of turn.
Airborne Adjudicator2WW
Creature - Human Knight Adviser (U)
Flying
As long as there are law counters on Airborne Adjudicator, creatures your opponents control with flying can't attack and can't block Airborne Adjudicator.
Proscribe 3 (This permanent enters the battlefield with 3 law counters on it. At the beginning of your upkeep remove a law counter from it.)
(2/3)
Bureaucratic DenialX1WU
Enchantment (R)
Bureaucratic Denial enters the battlefield with X law counters.
As long as there are law counters on Bureaucratic Denial opponents skip their draw steps.
During your end step gain life equal to the number of law counter on Bureaucrtic Denial.
Proscribe X (This permanent enters the battlefield with X law counters on it. At the beginning of your upkeep remove a law counter from it.)
Professional Mourner
Creature - Human (U)
Sacrfice Professional Mourner: Add 1 to your mana pool. This mana may only be used to cast spells and abilities from your graveyard.
Exsoul 1 : Exile Professional Mourner from your graveyard. Create a 1/1 White and Black spirit creature token with flying.
(1/1)
Spiritual Recruiter2
Creature - Spirit (R)
Lifelink
Whenever a creature is exsouled put a +1/+1 counter on Spritual Recruiter.
When Spiritual Recruiter enters the battlefield or is exsouled you may search your library for a creature with exsoul and put it into your graveyard.
Exsoul 2 : Exile Spiritual Recruiter from your graveyard. Create a 1/1 White and Black spirit creature token with flying.
2/2
I think its strength definitely hinges on how strong the artifacts are in your cube. I don't run swords or fast mana and so this guy is more middling to my 450 unpowered list, but probably still makes it anyway. Just haven't picked one up yet.
I've been playing a red/white boros mentor aggro build on MTG arena and I've been surprised by how much work Dual Shot has done. It picks off elves in Green Stompy, it kills early blockers to your threats like Glowspore Shaman, or does the last point of damage to multiple creatures in combat. I only run two, but they have been clutch in a lot of matchups. Also having a ton of success with Heroic Reinforcements. This has closed out so many games. Healer's Hawk has also been surprisingly effective.
Also Tajic, Aurelia, Warboss, Lightning Strike, Justice Strike, History of Benalia, and Rekindling Phoenix, but we already knew about these.
Watchlist Legion Warboss - Looks solid, but doesn't quite get there for me. Will watch. Nullhide Ferox - Non-creature spell drawback is too much. Tajic, Legion's Edge - Good card, but not convinced it is better than Aurelia and I'm not sure I want to cut Charm and Helix from Boros.
I think we've been waiting on the perfect black 5 drop for so long that it can't exist outside of a card that reads:
Black Wins4B
Creature - Winner (MR)
You may pay 0 instead of paying the casting cost of this card.
When Black Wins enters the battlefield, you win the game.
Who Cares what the p/t is.
Hyperbole aside....I think this is the best so far. It's an incredibly above-curve creature that even reanimator builds will pick up and it can dig for the other cards you need to win. When you put this next to Abyssal Persecutor you being to appreciate how disgustingly good this is...for 1 more you go from "you can't win and your opponent's can't lose" to the exact same stats and a repeatable ability to pay 2 life to fix your draws. I'm actually glad I still run persecutor because the cut is very easy here.
Explosive IdeaR
Sorcery (R)
Exile the top two cards of your library. You may play them this turn.
Jump-start (You may cast this card from your graveyard by discarding a card in addition to paying its other costs. Then exile this card.)
This is super pushed! I'm going to have to see what else this set has before figuring out how to rearrange these guilds.
Edit: Some (depraved) person on reddit just mentioned that this can go on an Isochron Sceptor...so for those of you still running that like I am....good times ahead!
My R/B section was Daretti, K. Command, Grenzo, and Falkenrath, I recently switched it to Daretti, K. Command, Dreadbore, and Vial Smasher. Grenzo is a bit mana intensive and the ability while INCREDIBLY fun, whiffs with some regularity. Falkenrath is solid, but I wanted some 2CC PW removal and Vial Smasher doesn't ask that you do anything but cast spells over the game. On rare occasion the requirement that you cast the more expensive spell first to take full advantage of him might be a hindrance, but this is a minor quibble. Also, Vial Smasher with Fireblast is disgusting.
Elspeth, Knight-Errant or Gideon, Ally of Zendikar
Only have room for one alongside 6CC Elspeth and 5CC Gideon
http://www.cubetutor.com/viewcube/34371
GU: Biomutate - When casting this creature you may return a creature you control to its owner's hand. If you do this enters the battlefield with +1/+1 counters equal to half of that creature's power rounded up.
RG: Overwhelm - If you control the creature with the greatest power, do X.
RB: Backlash - You may lose life equal to this card's converted mana cost when you cast this, if you do than do X
UW: Proscribe (X) - This permanent enters the battlefield with X law counters on it. At the beginning of your upkeep remove a law counter from it.
WB: Exsoul (Cost): You may exile this card from your graveyard. If you do create a 1/1 black and white spirit token with flying.
A few sample cards for fun.
Absorbing Ooze G
Creature - Ooze (U)
Biomutate - When you cast Absorbing Ooze you may return a creature you control to your hand, if you do Absorbing Ooze enters the battlefield with +1/+1 counters equal to half of that creature's power rounded up.
(0/0)
Whirlwind Lizard 3UG
Creature - Mutant Lizard (R)
Flash
You may return an opponent's creature as though it were under your control if using Whirlwind Lizard's biomutate ability.
Biomutate - When you cast Whirlwind Lizard you may return a creature you control to your hand, if you do Whirlwind Lizard enters the battlefield with +1/+1 counters equal to half of that creature's power rounded up.
(2/2)
Gruul Grunt 1R
Creature - Giant (U)
Overwhelm - If you control the creature with the greatest power during your end step, Gruul Grunt deals 1 damage to target creature an opponent controls.
(3/1)
Smash RG
Instant (R)
Target creature you control gets +2/+2 and trample until end of turn.
Overwhelm - If you control the creature with the greatest power you may have it deal damage equal to its power to target creature an opponent controls.
Blood Fencer 1RB
Creature (U)
Double Strike
Backlash - You may pay 3 life when Blood Fencer enters the battlefield. If you do it enters the battlefield with a +1/+1 counter.
(1/1)
Demonic Parade X
Sorcery (R)
Backlash
Create X 1/1 Black and Red demons with haste.
When you cast Demonic Parade, you may pay life equal to its converted mana cost. If you do, demons you control get +1/+1 until end of turn and gain "when this creature attacks it deals 1 damage to defending player" until end of turn.
Airborne Adjudicator 2WW
Creature - Human Knight Adviser (U)
Flying
As long as there are law counters on Airborne Adjudicator, creatures your opponents control with flying can't attack and can't block Airborne Adjudicator.
Proscribe 3 (This permanent enters the battlefield with 3 law counters on it. At the beginning of your upkeep remove a law counter from it.)
(2/3)
Bureaucratic Denial X1WU
Enchantment (R)
Bureaucratic Denial enters the battlefield with X law counters.
As long as there are law counters on Bureaucratic Denial opponents skip their draw steps.
During your end step gain life equal to the number of law counter on Bureaucrtic Denial.
Proscribe X (This permanent enters the battlefield with X law counters on it. At the beginning of your upkeep remove a law counter from it.)
Professional Mourner
Creature - Human (U)
Sacrfice Professional Mourner: Add 1 to your mana pool. This mana may only be used to cast spells and abilities from your graveyard.
Exsoul 1 : Exile Professional Mourner from your graveyard. Create a 1/1 White and Black spirit creature token with flying.
(1/1)
Spiritual Recruiter 2
Creature - Spirit (R)
Lifelink
Whenever a creature is exsouled put a +1/+1 counter on Spritual Recruiter.
When Spiritual Recruiter enters the battlefield or is exsouled you may search your library for a creature with exsoul and put it into your graveyard.
Exsoul 2 : Exile Spiritual Recruiter from your graveyard. Create a 1/1 White and Black spirit creature token with flying.
2/2
Let me know what you like!
Also Tajic, Aurelia, Warboss, Lightning Strike, Justice Strike, History of Benalia, and Rekindling Phoenix, but we already knew about these.
In
Doom Whisperer replacing Abyssal Persecutor
Assassin's Trophy replacing Lotleth Troll
Knight of Autumn - Moving Dryad Militant to Green. cutting Song of the Dryads.
Testing
Aurelia, Exemplar of Justice replacing either Boros Charm or Lightning Helix
Goblin Cratermaker don't have a cut yet.
Watchlist
Legion Warboss - Looks solid, but doesn't quite get there for me. Will watch.
Nullhide Ferox - Non-creature spell drawback is too much.
Tajic, Legion's Edge - Good card, but not convinced it is better than Aurelia and I'm not sure I want to cut Charm and Helix from Boros.
Black Wins 4B
Creature - Winner (MR)
You may pay 0 instead of paying the casting cost of this card.
When Black Wins enters the battlefield, you win the game.
Who Cares what the p/t is.
Hyperbole aside....I think this is the best so far. It's an incredibly above-curve creature that even reanimator builds will pick up and it can dig for the other cards you need to win. When you put this next to Abyssal Persecutor you being to appreciate how disgustingly good this is...for 1 more you go from "you can't win and your opponent's can't lose" to the exact same stats and a repeatable ability to pay 2 life to fix your draws. I'm actually glad I still run persecutor because the cut is very easy here.
Explosive Idea R
Sorcery (R)
Exile the top two cards of your library. You may play them this turn.
Jump-start (You may cast this card from your graveyard by discarding a card in addition to paying its other costs. Then exile this card.)
Edit: Some (depraved) person on reddit just mentioned that this can go on an Isochron Sceptor...so for those of you still running that like I am....good times ahead!