msem-instigator

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.

Whenever an opponent casts a spell, that player gets a poison counter unless they pay {1}.
As long as an opponent has five or more poison counters, Corrupted Soothsayer gets +2/+1 and has flying.

This spell can't be countered.
Tap up to three target permanents.
Coalesce {9}{U}{U} (You may cast this from your graveyard for {9}{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.)
Opponents can't untap more than two permanents during their untap steps while Drown Amidst the Cosmos is on the battlefield.

Flash
{U}, Put Elusive Hunter into its owner's library second from the top: Counter up to one target spell unless its controller pays {2}.

Target player shuffles up to three target cards from their graveyard into their library.
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

Whenever you draw your second card each turn, put a +1/+1 counter on Ethereal Sneak.

Search target opponent's library for a nonland card. You may cast that card without paying its mana cost. Then that player shuffles.
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

Whenever you draw your second card each turn, draw a card.

This spell costs {2} less to cast if its target's controller is poisoned.
Counter target spell unless its controller pays {X}.

You may reveal a Revelation card you own from outside the game or choose a face-up Revelation card you own in exile. Put that card into your hand. Exile From Stars Above.

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.
Untap each Horror you control during enchanted creature's controller's untap step.

Flying
When Helar Ritualist enters or whenever you cast a spell, if {W}{B} was spent to cast it, each opponent loses 3 life and you gain 3 life. Put a +1/+1 counter on Helar Ritualist.

The next time you cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

Create a 1/1 blue Illusion creature token with “This gets +1/+1 for each other Illusion you control.”
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

Defender
When Mnemonic Wall enters, you may return target instant or sorcery card from your graveyard to your hand.

Flying

Scry 1, then draw a card.
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

When Seeker of Communions enters, choose target player. If that player is poisoned, draw a card. Otherwise, that player gets a poison counter.

Serene Hart can't be blocked by creatures with power 4 or greater.

Flying
Whenever Sinewed Wings deals combat damage to a player, you may discard your hand. If you do, draw a card for each creature with flying you control.

At the beginning of each opponent's end step, if no spells controlled by that player resolved this turn, create a 1/1 blue Illusion creature token with “This gets +1/+1 for each other Illusion you control.”

Target player mills three cards for each poison counter they have.

Return target permanent to its owner's hand. If this spell wasn't cast from your hand, put that permanent on top of its owner's library instead.
Coalesce {9}{U} (You may cast this from your graveyard for {9}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Each player mills four cards.
Coalesce {5}{U}{U} (You may cast this from your graveyard for {5}{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.)
When A Vision Too Vast enters, you may cast target noncreature, nonland card with mana value 4 or less from a graveyard without paying its mana cost.

Enchant permanent
Whenever enchanted permanent becomes untapped, its controller gets a poison counter.