msem-instigator

Whenever you cast an instant or sorcery spell, you may exile that card instead of putting it anywhere else as it resolves.
At the beginning of your upkeep, Clash Reactor deals X damage to each opponent, where X is the number of colors of cards exiled with Clash Reactor.

Clash at Geier Reach deals 2 damage to each opponent and to each creature and planeswalker they control.
Cycling {2} ({2}, Discard this card: Draw a card.)

Target creature fights another target creature. (Each deals damage equal to its power to the other.)

Enchant creature
When Claustrophobia enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

This spell costs {1} less to cast for each card you've discarded this turn.
Draw three cards.

Cleansing Brimstone deals 2 damage to any target. If a creature or planeswalker dealt damage this way would die this turn, exile it instead.

Return target nonland permanent to its owner's hand.
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.)

Target creature you control gets +1/+1 until end of turn. It deals damage equal to its power to target creature you don't control.

Exile target nonland permanent.

{T}, Pay 1 life: Add {W} or {U}.
{1}, {T}, Sacrifice Cleared Vault: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Cleave deals 1 damage to each opponent and 1 damage to each creature and planeswalker your opponents control.

Return target creature you control and target creature you don't control to their owners' hands.

Cast this spell only during your turn.
Draw a card. Then if an opponent cast a spell this turn, scry 1 and draw an additional card.

Cliffside Entrance enters tapped unless you have 15 or less life.
{T}: Add {R} or {W}.

Choose target creature you control. Double its power and toughness until end of turn. That creature deals X damage divided as you choose among any number of target creatures and/or planeswalkers your opponents control, where X is its power.

Equipped creature has flying.
Equip {3}

When Climber's Outfit enters, search your library for a basic land card, reveal it, put it into your hand, then shuffle.
Equipped creature has reach.
Equip {1}

When Climbing the Oldest Mountain enters, draw a card, then choose a card name.
Whenever a creature you control with the chosen name deals combat damage to a player, put two +1/+1 counters on it.

Create a 2/2 black Zombie creature token.
Tether (Then if you cast this from your hand, you may exile it tethered to a creature you control. When it dies, you may cast this from exile without paying its mana cost.)

Target creature gets -4/-4 until end of turn.

Equipped creature has hexproof. (That creature can't be the target of spells or abilities your opponents control.)
Equip {0}

{T}, Tap an untapped creature you control: Choose one —
• Add one mana of any color.
• Target player loses 2 life.
• Target player gains 3 life.
• Target player mills four cards.

Clocktower Hideout enters tapped.
When Clocktower Hideout enters, look at the top card of your library. You may put it into your graveyard.
{T}: Add {B} or {R}.

Create a 0/0 blue Construct artifact creature token. Put X +1/+1 counters on it, where X is one plus the total number of noncreature, nonland cards in your graveyard.

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.)
Tap four untapped creatures you control: Unlock Clockwork Astrolarium. If the revealed card is white, put it into your hand. Otherwise, put it on top of your library.