The site was expected to shut down late last year, but got grabbed by somebody else at the last second. After the replacement, MTG Nexus, started up. Go there for a not-dead custom card community, it needs the traffic because it seems that a bunch of the people here didn't make the move.
Edit: Also pretty sure they're a bot, since here they say they're from Northern Ireland, but their other post uses a different site to say they're from Orlando, Florida. That other post was also really weird, talking about accessing this web site as a "download" you have to actively attempt, and are talking about MTG in weirdly archaic video game terms ("where to download the most recent release"? What is this, 1995?).
I'd focus on generating some new synergies between White and Red, beyond the existing Boros mechanics. As an example, here's some cards that open up some key roads to viability:
Scouring Insight2RR
Sorcery
Draw three cards, then reveal those cards. Discard any you don't play at the beginning of the next end step.
Impulsive draw that actually draws, then discards at the end of turn. Triggers Madness, puts things in the graveyard instead of Exile, but ultimately still in Red's thematic wheelhouse, even if it doesn't quite fit the existing mechanics. Less mana-efficient, but potentially more value-efficient for permitting graveyard synergies that are primary sources of value in Commander.
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Ceaseless Guardianship1WW
Enchantment
Enchant Creature
When you cast Ceaseless Guardianship, you may put a creature from your graveyard onto the battlefield. If you do, put a -1/-1 counter on that creature and attach Ceaseless Guardianship to it.
Enchanted creature has +0/+1, Persist, and "This creature must be assigned combat damage first if able".
When Ceaseless Guardianship is no longer attached to a creature, sacrifice that creature.
Usually better than Animate Dead proper (forcing damage to go through it first on the block can be a big help), but being in White gives it access to a lot of potential upsides, as White has Enchantment fetching and recursion. Alongside flickers to break the tie that'd make you sacrifice it. In this case, you can flicker the enchantment itself and attach it to another creature, keeping it if the creature doesn't have a -1/-1 counter on it. White also has plenty of ability to grant +1/+1 counters to reset the Persist, if you can keep supplying the Aura to grant it.
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Casualty Reserves1WWRR
Enchantment
Each creature card in your graveyard has Unearth 2WR and you may Unearth whenever you could play an Instant. 2W: Shuffle target creature card in your graveyard into your library.
So, funny thing with this card: Unearth already exists in Red, but a lot of the uses of it for White are blocked by that Sorcery speed restriction. So making Unearth an Instant is often going to be a White effect in nature, as its most obvious use is instant-speed blockers. And, of course, you can flicker the Unearthed creature to keep it. The shuffle-recovery means you're able to be in far less danger of decking out, counteracting mill and your own looting/rummaging, alongside the obvious return of a creature and having it exit graveyard hate territory.
---
Requisition SuppliesxxWR
Sorcery
Convoke
You may search your library for any number of equipment, reveal them, and put them into your hand, put any number of 1/1 White Human Soldier creature tokens onto the battlefield tapped and create any number of Treasure tokens.
The sum of the number of the equipment searched for, the number of creature tokens put onto the battlefield and the number of Treasure tokens created may not exceed X.
This is basically a "I need All The Stuff" card, letting you fetch out for Voltron pieces, making a fat board, or banking mana for a big play. Being two-X means that it's not useful early, but also excuses such a powerful effect as X-cost fetching (of course, compared to Stoneforge Mystic...), as well as being able to stock a fraction of your entire mana base with full fixing. And, of course, tossing out X bodies can easily be its own threat in Boros colors, home of a lot of board-wide buffs.
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These are mechanics to think about more than serious card suggestions. White getting shuffle-revival and Animate Dead style effects, slower and more fragile styles of reanimation than Black tends to work with, offers it the ability to recover resources without actually accelerating much. Things that provide recursive mechanics like Persist or Unearth help out, as well, as Boros is rather high up there for loving recursion. Lot of ETBs, dies and high-Power to amplify with recurring creatures.
Red getting better methods of card access for worse prices also helps significantly, where you can get a lot out of such a "staggered looting" or impulse draw from various discard effects if you're looking for them. Red is also supposed to be the home of ritual effects, but those have largely been phased out of the game, and oddly enough replaced with the stockpiled Treasures. Which also exist on some White taxes, like Smothering Tithe.
Generally, I want White to be the slow color of the game, continuing to lack acceleration, but making up for it with a good deal of recursion and a generally good baseline of value, alongside slowing others down. A lot of higher-color-identity cards are involved in this desire, as well. More taxes, generally in the vein of Smothering Tithe, alongside counterspells that are one-off prison and tax effects.
Gilded Lotus is one color at a time, though, as is Astral Cornucopia, so being two-color means it doesn't go infinite off those alone. You need some infinite filter to do it at two, and the "standard rate" tends to be about 3 mana anyways. So 1GU seems fine, bit of a danger when you get ability copies or discounts involved, but there's not many such effects that'll recur reliably, making it a low-reliability combo unless you really dive into it.
If the "theme" is landscape shifting and bending mana around, another ability could be a Scapeshift effect, alongside some form of color-hacking ability. Maybe use Islandhome and Forestwalk, then the hacking ability lets you mess with the creature's keywords to match the opponent you want to hit?
The big thing is that there's a lot of zero-mana artifacts already, and most of them are Equipment. Which Puresteel Paladin and other equipment synergies make a genuine problem. Furthermore, may of the issues with free artifacts care that you'd get a lot of them, which Artifact Lands act as one extra per turn, and have the opportunity cost of not being able to play another land of any kind any turn you play one. Which, if they're taplands, means being a mana behind whenever you play one.
Anything that involves sacrificing it is actually sacrificing a land, with the practical ongoing effect of one less mana per turn. No matter how you frame it, it's always going to be an opportunity cost of playing this instead of a more normal land, or a different zero-mana Artifact that could, potentially, be more useful like Mox Diamond or Mox Opal.
The clause could just be "X counters remain on ~ when it goes from the command zone to the battlefield", neatly excluding all other zone changes and counter types in the process.
Direct artifact lands could work, if they were lands with downside in some sense, as the issue with the original cycle has a lot more to do with the fact that they were Moxen that ate your basic land slot, while Affinity was at full power. Metalcraft continues the issues of allowing Artifacts instead of lands. I could perfectly well see a cycle of Artifact lands treated like duel-lands, perhaps modeling after the BFA allied-colored duel-lands, where they come into play tapped if you control less than two basic lands, which pressures for multicolor to stick to "splashes" rather than being heavily in need of fixed colors. And, in this case, against piling up non-basic lands like Darksteel Citadel to further press the advantage of having multi-typed lands.
The reason I didn't have the tutored card revealed is because I templated off the black Tutors, which don't have that clause. Didn't realize that was a feature of black Tutors and not part of standard Tutor properties. And in general, tutor color is about what the color cares to get. The Red is in the pseudo-randomness of needing to get something you haven't accessed yet (burning through options), the Blue is in the emphasis on one-off solutions (the core of many of its victory conditions is such combos).
As for the currently-nameless Council of One, being Flying and Trample and draw-double-for-damage and P/T being twice the cards you have in hand means that it reliably draws through enormous chunks of your deck, while it easily gets ahold of enough to be a severe beater with being in Green (tutor-based ramp) and Blue (directly drawing). It's a very reliable three-turn win unless you've been topdecking or the enemy's running a huge amount of Flyers.
If it was one P/T per card, it'd be fine because then it's tripling, instead of quintupling, hand size for the P/T of the initial hand size. One damage gets through, draw two cards, this thing gets +4/+4. That's too fast a buildup, it has to be fully blocked every time or else it trivially becomes too large to stop. Get rid of Trample or Flying, it becomes reliably blockable, instead of needing to be able to handle its full power every single turn or needing that line in the air. Did I mention that Blue can give unblockable to one-off free-hit? For +4/+4 per damage dealt? Make it draw one, the growth slows to reasonable levels, it doesn't constantly overfill your hand and it still has a reliably useful baseline P/T.
Gravetender ApostleWB
Creature - Human Cleric (u)
A deck may have any number of creatures named Gravetender Apostle.
1WW, sacrifice X Human Clerics you control: Search your deck for an Angel or your Graveyard for a Human or Spirit with converted mana cost X, then put it onto the battlefield tapped. 1BB, sacrifice X Human Clerics you control: Search your deck for a Demon or your graveyard for a Zombie or Skeleton with converted mana cost X, then put it onto the battlefield tapped.
1/4
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The fact it can recover humans from the graveyard is why I say differently abusive, because it can, with enough expense, recover a lot of nasty things, and there's some ways to fund it with tokens (Westvale Cult Leader being a big one). The higher mana costs are to respect the tutor and reanimation value, regardless of CMC, and it being any Human Cleric means you don't need to stack it indefinitely. The exact CMC match is to prevent over sacrificing for mass death triggers like Blood Artist. Or, more appropriately, Wayward Disciple.
It's also a useful creature, independently of the need to stack them like mad, because it has a good stat line for holding the board away from your face, and cheep enough to actually get there against aggro. As does the ability to sac any Human Clerics you have, not just the Apostles, their rule-of-4 bypass lets them be filler and more consistently gotten rather than being required for the ability, as you can instead sacrifice stuff like Banisher Priest to get to a game-winning Angel or Demon. And it lets you get Containment Priest and the like out of the way of your shenanigans, or sac now-dying Human Clerics to revive other cheap Human Clerics.
Except we already have Conspire, which is tap two color-sharing creatures per copy. Upgrading it to one creature of any kind very swiftly becomes abusive in any situation with decent token pumping, so the mechanic could never be printed alongside.
Adding a condition to the creatures that may tap to it, such as requiring the tapped creature to be a Dancer or have CMC, Power or Toughness match the cost of the Sorcery/Instant, would allow this to be more open. Having it be a variable for number of creatures to tap instead of, or even in addition to, the conditions. Maybe have it be allowing you to tap up to that many creatures, then it comes back if you meet that number, so you can set off Dancers with high-number Perform cards if you don't have enough to buy it back.
Something like this:
Perform X (You may tap up to X creatures you control with converted mana cost equal to or greater than this spell as an additional cost to cast this spell. If you tap X creatures this way, Exile it, then return it to your hand at the start of your next turn)
Having them only come back at the start of your next turn makes it able to be printed on a lot more effects, because you can't keep casting it as long as your mana and board holds out.
Tying into the converted mana cost requirement, Dancers could have a number of CMC-increasing mechanics on them, such as (2/W)(2/U)(2/B)(2/R)(2/G) mana symbols and refund mechanics like untapping lands, reducing costs and getting Treasure tokens. This would then be permissive of cards like Chord of Calling (though obviously more on the tutor side of things) that would otherwise be too heavy on combo options by having the major combo pieces have much higher CMCs than their casting costs. Can also have Split cards, to further promote this, as their CMC is that of the two sides combined. Could even bring back the Kamigawa Flip card frame for access to split permanents with the same CMC inflation property.
The big thing is that this is highly reliant on the environment, as it has no tap and is utterly generic costs. It's the next best thing to perfect color fixing, and allows you to ramp off of token generation. The non-rotating formats, to my knowledge, don't have any competitive token floods to fuel it for even more mana outside infinite combos that win the game already or are used to fuel more useful engines than just endless mana, restricting it to sacrificing your board to fund something else.
If there's good low-cost token generation, this gets broken. If there's a lot of recursion on permanents, this gets broken. If there's a lot of generic mana flying around and a wonderful toolbox environment, this gets broken for color-fixing. Basically, if the costs are trivialized, which has happened before (stick it alongside Urzatron and watch the toolbox fly), it turns into an enormously powerful engine for color consistency if you have a lot of generic mana, and an engine for that mana if you have a lot of permanents.
Actually an effect pruned from a card I posted in The Commander's Tools:
Exotic Tutor2(U/R)(U/R)
Creature - Goblin Advisor
When Exotic Tutor comes into play, search your library for a card that does not share a name with any permanents you control, any cards in your hand or any cards in your graveyard, put that card into your hand, then shuffle your library.
2/2 Why bother trying the same thing twice?
---
It's a terrible creature, in terms of the vanilla test. In Commander, it's Diabolic Tutor on a stick in Izzit colors, and therefor separated from much of what could recur it unless you go three colors (and also the colors to make it as bad as possible to be a Sorcery or Instant). In non-singleton formats, it's a way to fetch cards you haven't seen yet, but cannot get redundant cards, making it good for Superfriends and combos, but incapable of getting you extras after counters or removal take away the first, unless it was by Exile.
Lost1UU
Instant
Exile target attacking creature, then return it to the battlefield at the end of turn.
Fuse
////
Found2UU
Sorcery
Choose one:
Return target card you own in Exile to your hand
Search your library for a card that does not share a name with any permanents you control, any cards in your hand or any cards in your graveyard, put that card into your hand, then shuffle your library.
Fuse
---
As an explanation, I'm pretty sure the rules have it so that the CMC of a split card is the total of it, so this is a CMC 7 card, typically unplayable unless it wins you the game outright. But that's Atemsis's job, by hitting the enemy while you have six different CMCs in hand, so it fills you that slot with two options to assist this at playable costs. Lost keeps him from getting killed by a combat trick of any kind when you go in for the kill, including hard removal cast during an attack.
Found lets you get a non-duplicate, reliably offering another CMC regardless of format while disallowing the use of it to stack up copies of one card in non-Singleton formats (it's just a four-cost anything-other-than-basic-land tutor in singleton), and it can recover Aftermath cards like Commit // Memory that have stupidly powerful effects to recur and enormous CMCs, in addition to working around Exile removal (contrast the often-two-mana Wishes that get sideboard access, but generally have a downside). Diabolic Tutor, for reference on the fetch. Options send it high, but in singleton, it's not too bad, and in non-singleton, it restricts what you can get by a lot
It's fine. I was actually expecting more of a Bant tutor-ramp card than a Jeskai tutor-cloner, as Green Slivers are generally more necessary than Red Slivers, but this works great, too.
Stergos Cavern-TillerSSGGUU
Legendary Snow Creature - Wurm
Trample
Each time you tap a land, put a +1/+1 counter on Stergos Cavern-Tiller
Sacrifice a non-Snow land: Search your library for a Snow land that can produce at least one color of mana the sacrificed land could and put it onto the battlefield.
Sacrifice a Basic Snow land: Search your library for a non-basic land and put it onto the battlefield tapped.
6/4
Next: (derp, mixed up Commander-related threads) A Blue, but not Green, Ramp commander
Circle of Reflection2W
Enchantment 2W: Creatures you control become the color of your choice until end of turn, and you and your creatures gain Protection from that color until end of turn. Additionally, you may have creatures you control keep their other colors or lose a color of your choice until end of turn.
Thantis, the Skyblaze2BRG
Legendary Creature - Spider
Reach, Vigilance
When Thantis, the Skyblaze enters the battlefield, each creature with Flying fights another creature you don't control.
3/5
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Next: A non-WUBRG Commander that works for Slivers, but doesn't have Tribal effects.
Reyan Sword-Saint1WW
Creature - Human Cleric
Vigilance
Whenever a creature attacks you or a Planeswalker you control while Reyan Sword-Saint is in the graveyard, you may pay 3WW. If you do, return it to the battlefield transformed, then it Fights that creature.
4/2 For the whole of his life, he held the stories of Reya Dawnbringer as his guiding truths.
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Serran Guardian
(W) Creature - Angel Soldier
Flying, Vigilance
When Serran Guardian leaves the battlefield, you may pay 3WW. If you do, return target creature card with converted mana cost five or less from your graveyard to the battlefield and return Serran Guardian to your hand.
4/4 For two-hundred generations, he has ensured Serra's sacrifice was not in vain.
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The balancing thought is that it takes a lot to recur the revival. You have to cast Reyan Sword-Saint again for three mana, get it killed, pay five to return Serran Guardian (with a 4/4 Fight), then get that killed (can just Fight something with 4 or more Power) and pay another five to get the revival. Thirteen mana and two deaths to deal four damage to a creature and revive a CMC five or less creature.
The tie-in is that Sephara likes to run a lot of board wipes, since it's a high-Flying mono-white creature-focused deck that'll ignore most of the damage and just re-cast Sephara with the alternate cost. So you can reliably kill the sword-saint to get a grave-castable Serra Angel to Fight an attacker, with the option to instead return it to hand to recover a different CMC 5 creature, at the cost of needing to go through Reyan Sword-Saint again... Which, if you have a board wipe lined up, is just fine.
https://mtg.gamepedia.com/Compleation[/quote]
...The etymology geek in me is disappointed to learn of this only today. And I kinda still prefer the more usual spelling/meaning so that it can be used elsewhere, rather than limiting the mechanic specifically to Phyrexia. Using Compleat for a level-up or transform variant would work out better, as it'd specifically be related to the Artifact Creature change, and wouldn't be as conflicting with Proliferate and Infect in the same set, as a single -1/-1 counter disables some major value effects, and any Incompeatness causes the creature to wither away pretty quickly.
Conversely, if there's a separate counter that ticks up, then Proliferate can be used to accelerate it and Infect doesn't disable it outright. Which is of questionable lore validity, given that Infect is supposed to be Phyresis, which the Compleated are supposed to be already totally consumed by.
When someone thinks they're giving you a spelling lesson, but actually just doesn't know the reference.
Kidding aside, adding yet another layer of complexity to the mechanic by being able to cast creatures with incompleat as artifacts or non-artifacts is not what I'm aiming for. Incompleat already makes creatures better in that it gives them a range of different casting windows, being an artifact and by extension being susceptible to more removal helps balance this advantage. Thanks for your feedback.
That'd be why I'd suggested the inverse of it as a level up variant (card frame shifting towards colored-artifact as it goes down?) or subset of Transform, so that some of the fetching stuff seen with Birthing Pod could be present without becoming extremely nasty with these creatures (mind, the effect is, in general, a pain in the ass to ever balance, but I would rather the mechanics not make such effects even more broken). Artifact Creatures have a ton of vulnerability, as Artifacts are often much more in need of and subject to dedicated removal than creatures, meaning that anything like this that's a keystone isn't going to work very well. And, as mentioned above, the -1/-1 counters cause there to be difficulties with Infect and Proliferate in the same set.
Edit: Also pretty sure they're a bot, since here they say they're from Northern Ireland, but their other post uses a different site to say they're from Orlando, Florida. That other post was also really weird, talking about accessing this web site as a "download" you have to actively attempt, and are talking about MTG in weirdly archaic video game terms ("where to download the most recent release"? What is this, 1995?).
Scouring Insight 2RR
Sorcery
Draw three cards, then reveal those cards. Discard any you don't play at the beginning of the next end step.
Impulsive draw that actually draws, then discards at the end of turn. Triggers Madness, puts things in the graveyard instead of Exile, but ultimately still in Red's thematic wheelhouse, even if it doesn't quite fit the existing mechanics. Less mana-efficient, but potentially more value-efficient for permitting graveyard synergies that are primary sources of value in Commander.
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Ceaseless Guardianship 1WW
Enchantment
Enchant Creature
When you cast Ceaseless Guardianship, you may put a creature from your graveyard onto the battlefield. If you do, put a -1/-1 counter on that creature and attach Ceaseless Guardianship to it.
Enchanted creature has +0/+1, Persist, and "This creature must be assigned combat damage first if able".
When Ceaseless Guardianship is no longer attached to a creature, sacrifice that creature.
Usually better than Animate Dead proper (forcing damage to go through it first on the block can be a big help), but being in White gives it access to a lot of potential upsides, as White has Enchantment fetching and recursion. Alongside flickers to break the tie that'd make you sacrifice it. In this case, you can flicker the enchantment itself and attach it to another creature, keeping it if the creature doesn't have a -1/-1 counter on it. White also has plenty of ability to grant +1/+1 counters to reset the Persist, if you can keep supplying the Aura to grant it.
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Casualty Reserves 1WWRR
Enchantment
Each creature card in your graveyard has Unearth 2WR and you may Unearth whenever you could play an Instant.
2W: Shuffle target creature card in your graveyard into your library.
So, funny thing with this card: Unearth already exists in Red, but a lot of the uses of it for White are blocked by that Sorcery speed restriction. So making Unearth an Instant is often going to be a White effect in nature, as its most obvious use is instant-speed blockers. And, of course, you can flicker the Unearthed creature to keep it. The shuffle-recovery means you're able to be in far less danger of decking out, counteracting mill and your own looting/rummaging, alongside the obvious return of a creature and having it exit graveyard hate territory.
---
Requisition Supplies xxWR
Sorcery
Convoke
You may search your library for any number of equipment, reveal them, and put them into your hand, put any number of 1/1 White Human Soldier creature tokens onto the battlefield tapped and create any number of Treasure tokens.
The sum of the number of the equipment searched for, the number of creature tokens put onto the battlefield and the number of Treasure tokens created may not exceed X.
This is basically a "I need All The Stuff" card, letting you fetch out for Voltron pieces, making a fat board, or banking mana for a big play. Being two-X means that it's not useful early, but also excuses such a powerful effect as X-cost fetching (of course, compared to Stoneforge Mystic...), as well as being able to stock a fraction of your entire mana base with full fixing. And, of course, tossing out X bodies can easily be its own threat in Boros colors, home of a lot of board-wide buffs.
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These are mechanics to think about more than serious card suggestions. White getting shuffle-revival and Animate Dead style effects, slower and more fragile styles of reanimation than Black tends to work with, offers it the ability to recover resources without actually accelerating much. Things that provide recursive mechanics like Persist or Unearth help out, as well, as Boros is rather high up there for loving recursion. Lot of ETBs, dies and high-Power to amplify with recurring creatures.
Red getting better methods of card access for worse prices also helps significantly, where you can get a lot out of such a "staggered looting" or impulse draw from various discard effects if you're looking for them. Red is also supposed to be the home of ritual effects, but those have largely been phased out of the game, and oddly enough replaced with the stockpiled Treasures. Which also exist on some White taxes, like Smothering Tithe.
Generally, I want White to be the slow color of the game, continuing to lack acceleration, but making up for it with a good deal of recursion and a generally good baseline of value, alongside slowing others down. A lot of higher-color-identity cards are involved in this desire, as well. More taxes, generally in the vein of Smothering Tithe, alongside counterspells that are one-off prison and tax effects.
If the "theme" is landscape shifting and bending mana around, another ability could be a Scapeshift effect, alongside some form of color-hacking ability. Maybe use Islandhome and Forestwalk, then the hacking ability lets you mess with the creature's keywords to match the opponent you want to hit?
Anything that involves sacrificing it is actually sacrificing a land, with the practical ongoing effect of one less mana per turn. No matter how you frame it, it's always going to be an opportunity cost of playing this instead of a more normal land, or a different zero-mana Artifact that could, potentially, be more useful like Mox Diamond or Mox Opal.
As for the currently-nameless Council of One, being Flying and Trample and draw-double-for-damage and P/T being twice the cards you have in hand means that it reliably draws through enormous chunks of your deck, while it easily gets ahold of enough to be a severe beater with being in Green (tutor-based ramp) and Blue (directly drawing). It's a very reliable three-turn win unless you've been topdecking or the enemy's running a huge amount of Flyers.
If it was one P/T per card, it'd be fine because then it's tripling, instead of quintupling, hand size for the P/T of the initial hand size. One damage gets through, draw two cards, this thing gets +4/+4. That's too fast a buildup, it has to be fully blocked every time or else it trivially becomes too large to stop. Get rid of Trample or Flying, it becomes reliably blockable, instead of needing to be able to handle its full power every single turn or needing that line in the air. Did I mention that Blue can give unblockable to one-off free-hit? For +4/+4 per damage dealt? Make it draw one, the growth slows to reasonable levels, it doesn't constantly overfill your hand and it still has a reliably useful baseline P/T.
Have a widened and differently-abusive Shadowborn Apostle:
Gravetender Apostle WB
Creature - Human Cleric (u)
A deck may have any number of creatures named Gravetender Apostle.
1WW, sacrifice X Human Clerics you control: Search your deck for an Angel or your Graveyard for a Human or Spirit with converted mana cost X, then put it onto the battlefield tapped.
1BB, sacrifice X Human Clerics you control: Search your deck for a Demon or your graveyard for a Zombie or Skeleton with converted mana cost X, then put it onto the battlefield tapped.
1/4
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The fact it can recover humans from the graveyard is why I say differently abusive, because it can, with enough expense, recover a lot of nasty things, and there's some ways to fund it with tokens (Westvale Cult Leader being a big one). The higher mana costs are to respect the tutor and reanimation value, regardless of CMC, and it being any Human Cleric means you don't need to stack it indefinitely. The exact CMC match is to prevent over sacrificing for mass death triggers like Blood Artist. Or, more appropriately, Wayward Disciple.
It's also a useful creature, independently of the need to stack them like mad, because it has a good stat line for holding the board away from your face, and cheep enough to actually get there against aggro. As does the ability to sac any Human Clerics you have, not just the Apostles, their rule-of-4 bypass lets them be filler and more consistently gotten rather than being required for the ability, as you can instead sacrifice stuff like Banisher Priest to get to a game-winning Angel or Demon. And it lets you get Containment Priest and the like out of the way of your shenanigans, or sac now-dying Human Clerics to revive other cheap Human Clerics.
Adding a condition to the creatures that may tap to it, such as requiring the tapped creature to be a Dancer or have CMC, Power or Toughness match the cost of the Sorcery/Instant, would allow this to be more open. Having it be a variable for number of creatures to tap instead of, or even in addition to, the conditions. Maybe have it be allowing you to tap up to that many creatures, then it comes back if you meet that number, so you can set off Dancers with high-number Perform cards if you don't have enough to buy it back.
Something like this:
Perform X (You may tap up to X creatures you control with converted mana cost equal to or greater than this spell as an additional cost to cast this spell. If you tap X creatures this way, Exile it, then return it to your hand at the start of your next turn)
Having them only come back at the start of your next turn makes it able to be printed on a lot more effects, because you can't keep casting it as long as your mana and board holds out.
Tying into the converted mana cost requirement, Dancers could have a number of CMC-increasing mechanics on them, such as (2/W)(2/U)(2/B)(2/R)(2/G) mana symbols and refund mechanics like untapping lands, reducing costs and getting Treasure tokens. This would then be permissive of cards like Chord of Calling (though obviously more on the tutor side of things) that would otherwise be too heavy on combo options by having the major combo pieces have much higher CMCs than their casting costs. Can also have Split cards, to further promote this, as their CMC is that of the two sides combined. Could even bring back the Kamigawa Flip card frame for access to split permanents with the same CMC inflation property.
If there's good low-cost token generation, this gets broken. If there's a lot of recursion on permanents, this gets broken. If there's a lot of generic mana flying around and a wonderful toolbox environment, this gets broken for color-fixing. Basically, if the costs are trivialized, which has happened before (stick it alongside Urzatron and watch the toolbox fly), it turns into an enormously powerful engine for color consistency if you have a lot of generic mana, and an engine for that mana if you have a lot of permanents.
Actually an effect pruned from a card I posted in The Commander's Tools:
Exotic Tutor 2(U/R)(U/R)
Creature - Goblin Advisor
When Exotic Tutor comes into play, search your library for a card that does not share a name with any permanents you control, any cards in your hand or any cards in your graveyard, put that card into your hand, then shuffle your library.
2/2
Why bother trying the same thing twice?
---
It's a terrible creature, in terms of the vanilla test. In Commander, it's Diabolic Tutor on a stick in Izzit colors, and therefor separated from much of what could recur it unless you go three colors (and also the colors to make it as bad as possible to be a Sorcery or Instant). In non-singleton formats, it's a way to fetch cards you haven't seen yet, but cannot get redundant cards, making it good for Superfriends and combos, but incapable of getting you extras after counters or removal take away the first, unless it was by Exile.
Instant
Exile target attacking creature, then return it to the battlefield at the end of turn.
Fuse
////
Found 2UU
Sorcery
Choose one:
Return target card you own in Exile to your hand
Search your library for a card that does not share a name with any permanents you control, any cards in your hand or any cards in your graveyard, put that card into your hand, then shuffle your library.
Fuse
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As an explanation, I'm pretty sure the rules have it so that the CMC of a split card is the total of it, so this is a CMC 7 card, typically unplayable unless it wins you the game outright. But that's Atemsis's job, by hitting the enemy while you have six different CMCs in hand, so it fills you that slot with two options to assist this at playable costs. Lost keeps him from getting killed by a combat trick of any kind when you go in for the kill, including hard removal cast during an attack.
Found lets you get a non-duplicate, reliably offering another CMC regardless of format while disallowing the use of it to stack up copies of one card in non-Singleton formats (it's just a four-cost anything-other-than-basic-land tutor in singleton), and it can recover Aftermath cards like Commit // Memory that have stupidly powerful effects to recur and enormous CMCs, in addition to working around Exile removal (contrast the often-two-mana Wishes that get sideboard access, but generally have a downside). Diabolic Tutor, for reference on the fetch. Options send it high, but in singleton, it's not too bad, and in non-singleton, it restricts what you can get by a lot
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Next: Grothama, All-Devouring
Stergos Cavern-Tiller SSGGUU
Legendary Snow Creature - Wurm
Trample
Each time you tap a land, put a +1/+1 counter on Stergos Cavern-Tiller
Sacrifice a non-Snow land: Search your library for a Snow land that can produce at least one color of mana the sacrificed land could and put it onto the battlefield.
Sacrifice a Basic Snow land: Search your library for a non-basic land and put it onto the battlefield tapped.
6/4
Next: (derp, mixed up Commander-related threads) A Blue, but not Green, Ramp commander
Enchantment
2W: Creatures you control become the color of your choice until end of turn, and you and your creatures gain Protection from that color until end of turn. Additionally, you may have creatures you control keep their other colors or lose a color of your choice until end of turn.
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Next: Thantis, the Warweaver
Legendary Creature - Spider
Reach, Vigilance
When Thantis, the Skyblaze enters the battlefield, each creature with Flying fights another creature you don't control.
3/5
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Next: A non-WUBRG Commander that works for Slivers, but doesn't have Tribal effects.
Creature - Human Cleric
Vigilance
Whenever a creature attacks you or a Planeswalker you control while Reyan Sword-Saint is in the graveyard, you may pay 3WW. If you do, return it to the battlefield transformed, then it Fights that creature.
4/2
For the whole of his life, he held the stories of Reya Dawnbringer as his guiding truths.
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Serran Guardian
(W) Creature - Angel Soldier
Flying, Vigilance
When Serran Guardian leaves the battlefield, you may pay 3WW. If you do, return target creature card with converted mana cost five or less from your graveyard to the battlefield and return Serran Guardian to your hand.
4/4
For two-hundred generations, he has ensured Serra's sacrifice was not in vain.
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The balancing thought is that it takes a lot to recur the revival. You have to cast Reyan Sword-Saint again for three mana, get it killed, pay five to return Serran Guardian (with a 4/4 Fight), then get that killed (can just Fight something with 4 or more Power) and pay another five to get the revival. Thirteen mana and two deaths to deal four damage to a creature and revive a CMC five or less creature.
The tie-in is that Sephara likes to run a lot of board wipes, since it's a high-Flying mono-white creature-focused deck that'll ignore most of the damage and just re-cast Sephara with the alternate cost. So you can reliably kill the sword-saint to get a grave-castable Serra Angel to Fight an attacker, with the option to instead return it to hand to recover a different CMC 5 creature, at the cost of needing to go through Reyan Sword-Saint again... Which, if you have a board wipe lined up, is just fine.
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Next: Gabriel Angelfire
...The etymology geek in me is disappointed to learn of this only today. And I kinda still prefer the more usual spelling/meaning so that it can be used elsewhere, rather than limiting the mechanic specifically to Phyrexia. Using Compleat for a level-up or transform variant would work out better, as it'd specifically be related to the Artifact Creature change, and wouldn't be as conflicting with Proliferate and Infect in the same set, as a single -1/-1 counter disables some major value effects, and any Incompeatness causes the creature to wither away pretty quickly.
Conversely, if there's a separate counter that ticks up, then Proliferate can be used to accelerate it and Infect doesn't disable it outright. Which is of questionable lore validity, given that Infect is supposed to be Phyresis, which the Compleated are supposed to be already totally consumed by.
That'd be why I'd suggested the inverse of it as a level up variant (card frame shifting towards colored-artifact as it goes down?) or subset of Transform, so that some of the fetching stuff seen with Birthing Pod could be present without becoming extremely nasty with these creatures (mind, the effect is, in general, a pain in the ass to ever balance, but I would rather the mechanics not make such effects even more broken). Artifact Creatures have a ton of vulnerability, as Artifacts are often much more in need of and subject to dedicated removal than creatures, meaning that anything like this that's a keystone isn't going to work very well. And, as mentioned above, the -1/-1 counters cause there to be difficulties with Infect and Proliferate in the same set.