msem-instigator

Whenever another creature or enchantment you control enters, you gain 1 life.
{3}{W}{W}, Pay 5 life: Castigated Sister becomes a 5/5 Angel Horror with flying. (This effect doesn't end at end of turn.)

Tithe (When this creature enters, you may tap three other artifacts and/or creatures you control.)
When Cataclysmic Preacher's tithe is paid, return target instant or sorcery card from your graveyard to your hand.

When Catacomb Dredger dies, return another target creature card from your graveyard to your hand.

Return target creature card from your graveyard to your hand. You may trigger a death knell of that card.

Catalina's Turf enters tapped.
When Catalina's Turf enters, you may mill two cards.
{T}: Add {B} or {R}.

You gain 5 life. Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
Flashback {2}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Choose one. If you're horrific, you may choose both instead. (You're horrific as long as you've sacrificed a permanent or discarded a card this turn.)
• Destroy target artifact.
• Catastrophic Crash deals 3 damage to target creature.

Return target tapped creature to its owner's hand. (Then exile this card. You may cast the creature later from exile.)

[+1]: Create a 1/1 red Human creature token with haste.
[–2]: Untap all creatures you control. Until end of turn, they gain “{T}: This creature deals 1 damage to each opponent.”
[–6]: You get an emblem with “Whenever a creature becomes tapped, this emblem deals 2 damage to any target and you gain 2 life.”

Whenever Cattish Bluestocking deals combat damage to a player, draw a card.
Attain {4}{U} ({4}{U}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Double strike

Renown 2 (When this creature deals combat damage to a player, if it isn't renowned, put two +1/+1 counters on it and it becomes renowned.)
Whenever Cauldish Arrogant becomes blocked by one or more creatures, reveal the top card of your library. Cauldish Arrogant deals damage equal to that card's mana value to each creature blocking it. Then put that card into your hand.

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
When Cauldish Cavalier becomes renowned, you may pay 2 life. If you do, draw two cards.

Infiltrate (Whenever one or more attacking creatures you control aren't blocked, this creature gets +1/+1 until end of turn.)

Other nonland permanents enter tapped.
Your opponents can't activate abilities of tapped permanents.

{1}{G}, Sacrifice Caustic Caterpillar: Destroy target artifact or enchantment.

When Caustic Lurker dies, target player loses 1 life.

Improve {1} ({1}: 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.)
Whenever one or more creatures crew Cavalier Deluxe Roadster, you may phase out up to one of those creatures.
Crew 1. Activate only once during each of your turns.

When Cave Eel enters, look at the top three cards of your library. Put one on top and the rest on the bottom in any order.

Vigilance, reach
Whenever Cave Spider blocks a creature with flying, Cave Spider gets +2/+0 until end of turn.

{T}: Add {C}.
{T}, Sacrifice Cave of Pleonexia: Destroy target nonbasic land an opponent controls. You and that player each create a Treasure token. Activate only as a sorcery and only if that land's controller controls four or more lands. (A Treasure token is an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Trample
Cavern Carver has haste as long as you control another creature with flash or haste.

Whenever Cavern Monstrosity attacks, exile the bottom card of your library. You gain life equal to its mana value.

Flying
Whenever Cavern Scourge attacks, you may exile a card from your graveyard. If you do, you gain 3 life.