msem-instigator

({T}: Add {U}.)
Cloudbank enters tapped.
When Cloudbank enters, target creature gains flying until end of turn.

Cloudcover Heights enters tapped unless you control a Forest.
{T}: Add {R} or {W}.

Counter target spell. If that spell is countered this way, put it into its owner's hand instead of into that player's graveyard. That player mills three cards.

({T}: Add {R}.)
As Cloudpeak Spires enters, you may pay 1 life. If you don't, Cloudpeak Spires enters tapped.
Basic lands you control have “{T}: Add {R}.”

Return target creature to its owner's hand.
Kindle 1—{U} ({U}, Exile this card from your graveyard: Create a 1/1 colorless Elemental creature token. Kindle only as a sorcery.)

({T}: Add {R} or {W}.)
Cloudsteel Summit enters tapped.
{1}, {T}: Add {R}{R} or {W}{W}.

When Cloven Forms enters, reveal the top three cards of your library. Put all creature cards revealed this way into your hand and the rest into your graveyard.
{5}{G}{G}{G}, Exile Cloven Forms: Put a creature card from or hand or command zone onto the battlefield. Create a token that's a copy of it, except the token isn't legendary.

Clutch Shot deals 2 damage to target creature or planeswalker. If you control six or more lands, Clutch Shot deals 4 damage instead.

{T}: Add {C}.
{1}: Clutch of the Coil becomes a 1/1 Snake creature with poisonous 2 until end of turn. It's still a land. (Whenever this creature deals combat damage to a player, that player gets two poison counters.)

{1}, {T}: Draw a card, then exile a card from your hand face down until Cluttered Study leaves the battlefield. (It returns to your hand.)
{3}, {T}: Shuffle Cluttered Study into its owner's library.

{T}: Add one mana of any color.
{T}: Put a charge counter on Coalition Relic.
At the beginning of your first main phase, remove all charge counters from Coalition Relic. Add one mana of any color for each charge counter removed this way.

({T}: Add {W}, {U}, or {B}.)
Coastal Dominion enters tapped.

Coastal Metropolis enters tapped unless you have 15 or less life.
{T}: Add {W} or {U}.

Target creature gets +4/+4 until end of turn. Create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”

Submerge each creature you control. At the beginning of the next end step, you may turn any number of face down creatures you control face up. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

When Cobbled Currency enters, discard a card, then draw a card.
{3}, Sacrifice Cobbled Currency: Discard two cards, then draw two cards.

Equipped creature has flying.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Target creature you control gains hexproof and indestructible until end of turn. If it's a Knight or Soldier, put a +1/+1 counter on it.

For each permanent type, choose up to one target permanent of that type. Exile each of those permanents, then return them to the battlefield under your control. They gain haste until end of turn. At the beginning of your next end step, those permanents' owners gain control of them.

Target player reveals two cards at random from their hand. You choose one of them. That player discards that card.

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Other artifacts you control have extort.
Whenever a spell you control resolves, if it was extorted three or more times, each opponent discards a card and you draw a card.

Embellish {2}{U} (If you cast this spell for {2}{U}, create a 1/1 blue Thopter artifact creature token with flying when it enters.)
{T}: Target player mills a card. If you control three or more artifacts, that player mills three cards instead.

Flash
Enchant creature
Enchanted creature gets -2/-2 and can't block creatures you control.

Tap target creature. It doesn't untap during its controller's next untap step.
Agonize (You may cast this card from your graveyard by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile this card.)

Creatures have “Whenever this creature attacks or blocks, it fights another target creature.”