msem-instigator

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

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

({T}: Add {B} or {R}.)
Whenever Crumbling Precipice becomes tapped, you lose 1 life unless you control two or more basic lands.

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.)

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

{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.

When Cryptic Waypoint enters, create a 1/1 blue Scout creature token.
{T}: Add {G}, {U}, or {R}.

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

({T}: Add {U} or {R}.)
Whenever Crystal Cavern becomes tapped, you lose 1 life unless you control two or more basic lands.

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

{T}: Add {C}.
{T}, Pay 1 life: Add {U} or {B}.

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.

Equipped creature has “{T}, Sacrifice this creature: Return target creature card from your graveyard to the battlefield.”
Equip {5}
Equip {1}{B}{B}

{T}: Add {C}.
{T}, Pay 1 life: Add {W} or {U}.

You may look at the top card of your library.
{T}: You may play the top card of your library.

At the beginning of your first upkeep each turn, choose one —
• Replace your first main phase this turn with an additional upkeep step.
• Replace your second main phase this turn with an additional combat phase.

{1}, Sacrifice Curious Fossil: Scry 2.
{2}{U}: Return Curious Fossil from your graveyard to the battlefield transformed. Activate only during your turn.

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}

{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.

({T}: Add {W} or {B}.)
Cursed Wastes enters tapped.
{1}, {T}: Add {W}{W} or {B}{B}.