msem-instigator

(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.

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.

When Cosmonaut Pioneer enters or leaves the battlefield, choose one—
• Scry 1, then draw a card.
• Create a 3/3 green Alien creature token with trample.
• You gain 5 life.

Siphon (Each -1/-1 counter you put on your creatures up to their remaining toughness while casting this pays for {1}.)
Costly Ambush deals damage equal to the greatest power among creatures you control to target creature or planeswalker.

Whenever another creature with power 2 or less you control enters for the first time each turn, you may pay {W}. If you do, draw a card.

As an additional cost to cast this spell, discard a card.
Draw two cards. The next card you foretell this turn costs {0} to foretell.

Wanderlust — This spell costs {2} less to cast as long as you control four or more differently named lands.
Crackle Across Kahembo deals X damage to target creature or planeswalker.

Enchant land
When Cradle of Civilization enters, search your library for a basic land card, reveal it, put it into your hand, then shuffle.
Enchanted land has “{T}: Add one mana of any color.”

Bloodprice—Reappropriate red. (You may cast this spell by sacrificing a creature and exiling two red cards from your hand and/or graveyard.)
Haste
Whenever Creed's Desperado attacks, if defending player has more cards in hand than you, exile the top card of that player's library. You may cast it as long as you control a Warrior, and you may spend mana as though it were mana of any color to cast it.

{T}: Add {C}.
{3}, {T}: Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

When Crescent of the Harvest Moon enters or whenever equipped creature attacks, exile up to one target card from a graveyard.
Equipped creature gets +1/+1.
{X}: Equipped creature becomes a copy of a permanent card with mana value X or less exiled with Crescent of the Harvest Moon until end of turn (even if this becomes unattached). Activate only as a sorcery.
Equip {2}

Cresting Bay enters tapped unless you control a basic Island.
{T}: Add {U}.
{2}{U}{U}: Until end of turn, Cresting Bay becomes a 3/3 blue Elemental creature with “Whenever this creature attacks, you may draw a card then discard a card.” It's still a land.

Tithe (As you cast this spell, you may tap three artifacts and/or creatures you control.)
Croakfolk Marsh-Baron enters with X +1/+1 counters on it. If its tithe was paid, it enters with twice X +1/+1 counters instead.

When Crooked Merchant dies, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Equipped creature gets +X/+X, where X is the number of cards in your graveyard.
Sacrifice a creature other than equipped creature: Equipped creature gains lifelink and indestructible until end of turn.
Equip {3}

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

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

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.

Foretell {B} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)
Up to one target creature gets -1/-1 until end of turn. Put a +1/+1 counter on up to one target creature.

I, II — Create a tapped Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
Discovery — {2}, Sacrifice an artifact: Draw a card.

Flash
Enchant player
When Curse of Ceaseless Pursuit enters, put two +1/+1 counters on target creature you control.
Creatures attacking enchanted player have trample.

Enchant player
When Curse of Grasping Air enters, enchanted player reveals their hand. You choose a nonland card from it. That player discards that card.
Spells you cast that target enchanted player cost {1} less to cast.

Enchant player
When Curse of Life's Cycles enters, destroy target creature enchanted player controls.
Concord — At the beginning of enchanted player's upkeep, if there are four or more card types among permanents you control, that player loses 1 life and you gain 1 life.

Enchant player
At the beginning of enchanted player's upkeep, that player upgrades a creature you control. (They give it one of the listed counters it doesn't have.)
• +1/+1
• Lifelink
• Menace

Equipped creature gets +2/+1.
When equipped creature deals combat damage to an opponent, you may sacrifice Cursebreaker Hammer. If you do, destroy target artifact or enchantment that player controls.
Equip {2}