msem-instigator

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell with a creature type no creature you control has.

You may play lands from your graveyard.

{2}, {T}: Draw a card. Crude Tablet doesn't untap during its controller's next untap step.

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

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 Vestige enters the battlefield tapped.
When Crumbling Vestige enters the battlefield, add one mana of any color.
{T}: Add {C}.

When Crux Pinnacle enters the battlefield, 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.

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.

Whenever you sacrifice a permanent, scry 1.
{1}, Sacrifice a nonland permanent: You gain 1 life.

Crystal Garden enters the battlefield tapped.
{T}: Add one mana of any color. You can't spend this mana to cast a creature spell.

When Crystalline Golem enters the battlefield, choose a color. You gain 1 life for each permanent of that color you control.

Equipped creature gets +2/+1 and has menace.
Whenever equipped creature deals combat damage to a player, they sacrifice two permanents.
Equip—{2}, Sacrifice a creature.

At the beginning of your first upkeep each turn, choose one —
• This turn, replace your precombat main phase with an additional upkeep step.
• This turn, replace your postcombat main phase with an additional combat phase.

Play with the bottom card of your library revealed.
Whenever you cast a spell or play a land from your hand that shares a type with the bottom card of one or more of your libraries, you may cast each of those cards without paying its mana cost or put it onto the battlefield if it's a land.

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}

{3}, {T}: Choose a card name, then reveal a card at random from your hand. If that card has the chosen name, Cursed Scroll deals 2 damage to any target.

Equipped creature has lifelink as long as it's white. The same is true for flying and blue, menace and black, first strike and red, and trample and green.
Equip {1}

Equipped creature gets +2/+2.
Equip {3}

Whenever Dancing Lion attacks, if it was crewed by two or more creatures in the same pack this turn, create a tapped and attacking token that's a copy of one of them. Sacrifice the token at the beginning of the next end step. (Two or more creatures you control with equal power are in a pack.)
Crew 2

Whenever equipped creature attacks, create a token that's a copy of it and that's tapped and attacking, except that token isn't legendary if equipped creature is legendary. Exile that token at end of combat.
Equip {3}

You may have Darksteel Mirror enter the battlefield as a copy of any permanent on the battlefield, except it has indestructible in addition to its other abilities.

When Darna's Grimoire enters the battlefield, you may discard a card. If you do, draw a card.
{2}, Sacrifice Darna's Grimoire: Draw a card.

Draw a card.

When Datalith enters the battlefield, conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)
{T}: Add one mana of any color.

{T}, Sacrifice Daunting Skyline: Search your library for a Plains or Swamp card and put it onto the battlefield tapped, then shuffle.