msem-instigator

{T}, Remove a +1/+1 counter from a creature you control: You draw a card and you lose 1 life.

({T}: Add {B}.)
Corpsebed enters tapped.
When Corpsebed enters, exile up to two target cards from graveyards.

Whenever another Zombie or Demon creature you control enters, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)

Menace
Whenever you cast an instant or sorcery spell, create a 2/2 black Zombie creature token. This ability triggers only once each turn.

When target creature you control dies this turn, return it or another creature card with an equal or lesser mana value from your graveyard to the battlefield tapped.

Return target creature or planeswalker card from your graveyard to the battlefield. If that card was a creature, it's an Actor in addition to its other types.

When Corrupt Warden enters, up to one target creature gets -X/-X until end of turn, where X is the number of card types among cards in your graveyard.

This spell costs {1} less to cast for each card type among cards in your graveyard.
Deathtouch

Flying
{1}{B}, {T}: Destroy target creature that was dealt damage this turn.

Rhapsody {5}{R}{R} (Pay {5}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
When Corrupted Guardian enters, it deals damage equal to its power to up to one target player or planeswalker.

Surveil 2, then you draw a card and you lose 1 life. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)
{2}{B}, Exile Corrupted Knowledge from your graveyard: Each opponent loses 2 life and you gain 2 life.

Glitch {1} (Remove one [restriction] for each time you pay the glitch cost.)
Target opponent reveals their hand. You choose a [noncreature,] nonland card [with mana value 3 or less] from among them. That player discards that card.

(Transform this if it's not attached to a creature. Pay {3}{B} as a sorcery to unattach it.)
Enchant creature you control
Corrupted Mount's rider gets +5/+4 and can't block.

Whenever an opponent casts a spell, that player gets a poison counter unless they pay {1}.
As long as an opponent has five or more poison counters, Corrupted Soothsayer gets +2/+1 and has flying.

Enchant creature
Enchanted creature gets +3/-2.

Enchant creature
Enchanted creature gets -3/-3 and has “At the beginning of your upkeep, you lose 3 life.”

Corsair Sellsword can't block.
Whenever you foretell a card or cast a foretold spell, you may return Corsair Sellsword from your graveyard to your hand.

Living weapon (When this Equipment enters, create a 0/0 black Phyrexian Germ creature token, then attach this to it.)
Equipped creature gets +1/-1.
Whenever equipped creature dies, draw a card. This ability triggers only once each turn.
Equip {1}

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
Corym's Elite can't be blocked by creatures with power 2 or less.

Reach
Improve {1}{G/W} ({1}{G/W}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on that creature instead.

Cosmic Catastrophe deals 6 damage to target creature or planeswalker. If you control a creature with power greater than its base power, Cosmic Catastrophe deals 3 damage to each opponent.

{T}: Add one mana of any color.
{5}, {T}, Sacrifice Cosmic Chart: Search your library for a card, put it into your hand, then shuffle.

Converge — Counter target spell unless its controller pays {1} for each color of mana spent to cast Cosmic Sinkhole.

Exchange control of target creature you control and target noncreature spell an opponent controls. You may choose new targets for that spell.

Purge, then you may tap an untapped creature you control. If you do, purge again. (To purge, exile two cards that share a type from graveyards. If you do, draw a card.)