msem-instigator

Destroy target creature.
Create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)

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.)

Crumbling Aqueduct enters tapped unless you control another Desert.
{T}: Add {U} or {B}.

Crumbling Necropolis enters tapped.
{T}: Add {U}, {B}, or {R}.

Crumbling Shrine enters tapped. When it does, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this, then you may put that card into your graveyard.)
{T}: Add {G}.
{2}{G}{G}: Crumbling Shrine becomes a Nymph creature. (This effect lasts indefinitely.)

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

Up to one target creature you control has base power 4 until end of turn. (Then exile this card. You may play the land later from exile.)

Primal {1}{B} (During your turn, you may cast this spell for {1}{B} instead of playing a land.)
Each opponent discards two cards.

Each opponent discards two cards. If you control a Knight or Soldier, each opponent loses 2 life and you gain 2 life.

Pressure {U}{U} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
Counter target spell.

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.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Crusher Beetle can't be blocked by more than one creature.

{1}{B}, Discard Crusher Claw: Target creature gains winnow until end of turn. (Damage dealt to it also causes its controller to lose that much life.)

Choose one —
• Destroy target artifact.
• Crushing Grip deals 2 damage to any target.

Enchant player
Whenever one or more creatures you control die, enchanted player loses 1 life and you gain 1 life.

Death knell — Put a trample counter on target creature you control. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)
Sacrifice a creature: Put a +1/+1 counter on Crushing Victor. Activate only as a sorcery.

When Crux Pinnacle enters, for each color, exile up to one target permanent of that color until Crux Pinnacle leaves the battlefield.
Whenever a player casts a spell, if there are five or more spells on the stack, you win the game.

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.

Deathtouch
When Crypt Strider enters, create a 1/1 black Skeleton creature token for each creature card in your graveyard.

Search your library for a card, exile it face down, then shuffle. For as long as that card remains exiled, you may cast it. It costs {2} more to cast this way if you don't control a legendary creature as you cast that spell.

{T}: Add {C}.
{X}: Crypt of Myriad Fates becomes a copy of target creature card with mana value X or less in your graveyard until end of turn, except it's 2/2 and a land in addition to its other types. Activate only outside of combat.

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
{1}, Discard two cards: Unlock Cryptic Fragment. If the revealed card is a basic land card, put it into your hand.

Cryptic Reef enters tapped.
{T}: Add {G} or {U}.
{2}{G}{U}, {T}, Sacrifice Cryptic Reef: Draw a card.

Reveal the top three cards of your library. Target opponent may have you put those cards into your hand. Otherwise, put those cards into your graveyard, then draw three cards.

When Cryptic Sentinel enters, attach any number of target Auras you control to Cryptic Sentinel.
{G}{W}, Sacrifice an Aura: Tap Cryptic Sentinel. It gains indestructible until end of turn.