msem-instigator

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.

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

({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}.

({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}.”

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

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.)

Return target creature to its owner's hand.
Coalesce {4}{U}{U} (You may cast this from your graveyard for {4}{U}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Coastal Cairn enters tapped. When it enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
{T}: Add {U} or {R}.

({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}.

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

Flash
Flying
When Cobblespook enters, tap target artifact or creature an opponent controls.

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.

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

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.)

Equipped creature gets +1/+1 and has vigilance.
Equip {1}

Destroy target artifact or enchantment with mana value 4 or less.

{T}: Add {C}.
{1}, {T}, Return Collapsing Ground to its owner's hand: Add one mana of any color.

{T}: Add {C}.
{T}, Pay 1 life: Add {B}.
{5}{B}, {T}, Sacrifice Collapsing Ridges: Return target creature card from a graveyard to the battlefield under your control. Activate only as a sorcery.

First strike

Whenever you draw a card, you may exile the top card of your library.
{3}{U}{U}, Sacrifice Collector of Memories: Shuffle your hand into your library, then put each card exiled with Collector of Memories into its owner's hand.

Creatures you control named Colocolo can't be blocked and have ward {2}.
{U}{U}: Put an inspiration counter on target creature. It's named Colocolo in addition to its other names for as long as it has an inspiration counter on it.