(2.5/3) Balance - Affinity for enchantments is still affinity, meaning this can come down early, which can be very strong despite the setup needed. That activated ability is potentially really powerful, after all. Believe it or not, I initially had it as a 5 mana card :)). I eventually moved it to ...

Votes: bravelion83, netn10 Tar-Baphon 2BBB Legendary Creature — Zombie Wizard (MR) When Tar-Baphon enters the battlefield, create X 2/2 black Zombie creature tokens, where X is the number of Zombies you control. When Tar-Baphon enters the battlefield, create a colorless Philactery artifact token wit...

Votes: bravelion83, Rithaniel

Brain Upload UU
Artifact (U)
You may have Brain Upload enter the battlefield as a copy of any creature on the battlefield, except it's not a creature.
The output drivers still need work.

Votes: netn10, Rithaniel

Ray of Diminution XU
Sorcery (U)
Creatures your opponents control get -4/-X until end of turn, where X is the amount of B spent to cast this spell.

Votes: Raptorchan, netn10

Distiller of Knowledge WUBRG
Creature — Eldrazi Wizard (R)
Devoid
When you cast this spell, add 5. When you spend all this mana this turn, draw three cards.
"Hm. That's probably more efficient than whatever I've been doing."
—Vel'koz
5/5

Votes: Raptorchan, netn10 Fan of Origin Winds 6 Legendary Artifact — Equipment (MR) Whenever equipped creature attacks, destroy all other tapped creatures, and tap all other untapped creatures. Equip—Sacrifice an Elemental "It's better to think of it as a portable, permanent Gate to the Maelstr...

Votes: netn10, void_nothing The Abyss Enchantment (MR) (Color indicator: black) Whenever a spell or ability an opponent controls causes you to reveal your hand while The Abyss is in your hand, that player reveals their hand. You choose a nonland card from it. That player discards that card. Cycling ...

Votes: void_nothing, netn10

Rooting Tree Spirit G
Creature — Dryad (R)
Whenever Rooting Tree Spirit deals combat damage to a player, it becomes a Forest.
Sentience isn't for everyone.
2/1

Votes: Raptorchan, netn10

Odd Condition WWW
Enchantment — Aura Curse (MR)
Enchant opponent
At the beginning of enchanted player's upkeep, put a flux counter on Odd Condition.
Enchanted player can't cast spells while the number of flux counters on Odd Condition is even. (0 is even)

Votes: Raptorchan, netn10

Gains from Trade 1WU
Enchantment (R)
Whenever you gain 4 or more life from a single source, draw a card.
At the beginning of your end step, gain life equal to half the mana you spent this turn.

Votes: RattingRots, Rithaniel

Rocks Fall B
Sorcery (R)
Destroy all creatures with 1 toughness.
//
Fuse
//
Everyone Dies 3BB
Sorcery (R)
This spell costs 1 less to cast for each creature that died this turn.
Destroy all creatures.

Synaptic Burst 2UR Sorcery Synaptic Burst deals damage to target creature or planeswalker equal to the number of cards in your hand. Psionic 1UR (You may cast this spell from your library for its Psionic cost while it's revealed.) Next: Suspiciously Cheap Mercenary R Creature — Human Warrior (U) Tr...

Votes: void_nothing, Rithaniel

No Singling Out U
Instant (U)
Counter target instant or sorcery spell with a single target.
There's a fine line between recursion and hypocrisy.

Votes: Raptorchan (cleanest design I've seen in a long time), RattingRots Amira, Atoned Succubus 1UU Legendary Creature — Demon Advisor (MR) Flying, protection from red Whenever a spell you don't control is countered, create a Treasure token. Sacrifice four Treasure tokens: Gain control of target cr...

Votes: Rithaniel, void_nothing Temporal Manomaly UR Enchantment (U) Whenever an instant or sorcery spell without targets is cast from a player's hand, exile it. At the beginning of the next end step, that card's owner may cast it from exile without paying its mana cost. I'll get back to you on that.

Votes: bravelion83 (being a cephalid itself is hilarious flavor), Komandon David's Sacrifice BG Instant (C) The creature with the lowest power you control deals damage equal to its power to the creature with the highest toughness target opponent controls. At the beginning of the next end step, you m...

I might be misreading the flavor text, but my impression at least is that the solitary plane of Genesis is sort of like a dnd-style pocket demiplane. Sort of like the place Nicol Bolas is trapped in. And the broader world that interfaces with Genesis is in fact open-ended.

@Rithaniel I just noticed that you assigned cards to players in a way that forms a connected digraph with a single cycle. Coincidence or purposeful? :D

Diana, Deathweave Hieromancer 4WB Legendary Creature — Human Wizard (MR) Affinity for enchantments Sacrifice an enchantment: Put a shield counter on target creature you control. Each opponent sacrifices a creature unless they sacrifice an enchantment. "I find the Keepers' lectures about humili...

Votes: bravelion83, netn10 Peacetime Training UW Enchantment (R) Creatures enter the battlefield with a langour counter on them. (A creature with a langour counter on it has base power and toughness 0/1 and "Whenever this creature attacks, remove all langour counters from it.". This is a p...

Votes: bravelion83, RattingRots 3WT, the Final Turbine 1UR Legendary Artifact Creature — Construct Weird (MR) Kicker—At the beginning of your next end step, you lose the game. When 3WT enters the battlefield, if it was kicked, it gains haste and "Whenever 3WT attacks, return target creature to ...

Votes: RattingRots, void_nothing

Leyline Pendant 4
Artifact (R)
When Leyline Pendant enters the battlefield, you may put a land card from your hand onto the battlefield.
T: Add one mana of any color a land you control can produce.
It reflects the energies deep within.

Votes: Komandon, void_nothing

Proxy Farming 2RR
Enchantment (Un-R)
Creatures you control can't be blocked.
Creatures your opponents control have "T: This creature fights target creature."
Big.

Votes: bravelion83, void_nothing

Dialectic 1WU
Enchantment (R)
Whenever an instant or sorcery with "destroy" in its rules text resolves, if no permanent was destroyed this turn, draw a card.

Votes: bravelion83, Rithaniel (supermarkets are lit)

Oath of Pizza 4RG
Enchantment (Un-MR)
Whenever you draw a card, deal combat damage to a player, play a land, or cast a planesalker spell, create a Food token.
Sacrifice 20 Food tokens: You win the game.
Almost everything in moderation.