msem-instigator

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.

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.

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.

Whenever one or more cards leave your graveyard, each opponent loses 1 life and you gain that much life.

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.

Sacrifice a creature: Each opponent loses 1 life and you gain 1 life.
Sacrifice two creatures: Draw a card.
Sacrifice three creatures: Exile target creature or planeswalker.

When Covert Reinforcement enters, exile target nonland permanent an opponent controls until Covert Reinforcement leaves the battlefield.

Flying
When Covetous Pixie dies, if you control another Angel, Demon, Faerie, or Spirit, put a -1/-1 counter on target creature an opponent controls.

Resolute — Whenever Crackling Agama deals combat damage to a player, if Crackling Agama's power is greater than its base power, that player sacrifices an artifact or enchantment.

{1}{R}, Sacrifice Crackling Seaform: Counter target spell unless its controller has Crackling Seaform deal 3 damage to them.

Trample, haste
All creatures able to block Crashing Mammoth do so.

Hexproof
Whenever one or more cards are put into your graveyard from anywhere, Creeping Hidebehind gets +1/+0 until end of turn.

Harmony — Target player mills four cards.
When Creeping Pianist enters, harmonize. (Trigger up to one harmony of one permanent you control.)

Haste
{R}{R}{R}, Discard your hand, Sacrifice Crimson Knight: Draw three cards.

Whenever another creature named Crinster Sheepdog enters, nourish 1. (To nourish 1, either put a +1/+1 counter on this creature or create a 1/1 white Citizen creature token.)

{T}, Tap two other untapped creatures you control: Add two mana of any one color.

Hexproof
Whenever an enchantment you control enters, draw a card.

Reach
Scarecrow spells you cast cost {1} less to cast.

Flying
Cruel Fledgling enters with a +1/+1 counter on it if six or more cards are in your graveyard.

Whenever Cruising Schooner attacks, it gets +1/+1 until end of turn.
Crew 1 (Tap any number of creatures you control with total power 1 or greater: This Vehicle becomes an artifact creature until end of turn.)

Creatures you control get +4/+4 and gain trample until end of turn.
Coalesce {8}{G}{G} (You may cast this from your graveyard for {8}{G}{G}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
Trample

Assault {3}{G} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
When Crushclaw Pulverizer assaults, you may destroy target artifact or enchantment.

Menace, haste, decayed (This can't block. When it attacks, sacrifice it at end of combat.)
At the beginning of combat on each of your turns, if you have three or more creature cards in your graveyard and haven't controlled a creature named Crypt Gnawer this turn, return Crypt Gnawer from your graveyard to the battlefield.

{2}{G}: Cryptozoologist voyages. (If it isn't blocking or targeted by another spell or ability, it phases out.)
Whenever Cryptozoologist phases in, you may put a creature card from your hand onto the battlefield until Cryptozoologist leaves the battlefield. (It returns to your hand if it's still on the battlefield.)