msem-instigator

Deception {1}{U} ({1}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Marilye deals combat damage to a player, you may search your library for an artifact card with mana value less than or equal to the amount of damage that player has been dealt this turn, put it onto the battlefield, then shuffle.

Colossal 4—{5}{U}{U}{U} (You may cast this for its colossal cost to have it enter with four +1/+1 counters; or pay {5}{U}{U}{U} as a sorcery: Put four +1/+1 counters on it if it has none.)
Whenever Megalokraken enters or attacks, reveal the top X cards of your library, where X is Megalokraken's power. You may cast a noncreature spell with mana value X or less from among them without paying its mana cost. Put the rest on the bottom of your library in a random order.

Transcend (Activate as a sorcery to gain the next type and a +1/+1 counter.)
Flying
{2}{U}{U}: Wizard — Draw a card, then discard a card. Mizuki gains “Noncreature spells you cast cost {1} less.”
{6}{U}{U}: Avatar — Draw two cards. Mizuki gains “Whenever Mizuki attacks, you may cast a noncreature spell from your hand without paying its mana cost.”

Look at the top two cards of your library. Put one of them into your hand and the rest into your graveyard.
Rerun (If you cast this from your hand, exile it as it resolves. Whenever a creature you control dies, you may cast this card from exile without paying its mana cost.)

Scry 1. Draw a card. Scry 1.

Flying, ward {2}
Whenever Realm Crossers deals combat damage to a player, create a blue enchantment token named Tambo with “At the beginning of your upkeep, draw a card if you control a Scout.”

Flash
Prowess
When Reconstructed Adept enters, target instant or sorcery card in your graveyard gains agonize until end of turn. (You may cast it by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile that card.)

When Rixia, Rift Shunted enters, target creature can't be blocked this turn.
Whenever a creature you control deals combat damage to an opponent, you may aetherize it. (To aetherize, create a token that's a copy of it, then exile that token.)

Counter target spell. Tap all lands that spell's controller controls and that player loses all unspent mana.

When Stillmarsh Brinecatcher enters, return another target nonland permanent to its owner's hand.
At the beginning of your end step, if you control a permanent with mana value 5 or greater, you may sacrifice Stillmarsh Brinecatcher. If you do, draw a card and create a 3/2 colorless Horror creature token.

Reveal the top four cards of your library. You may put one into your hand and the rest into your graveyard.
Compose (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

Discard a card: Unseen Maniac gets +1/+1 and can't be blocked this turn.
Whenever Unseen Maniac deals combat damage to a player, draw a card.

Until end of turn, you may cast creature spells as though they had flash.
Creatures you control can't be the targets of spells or abilities your opponents control this turn.

Counter up to one target spell unless its controller pays {2}. Until end of turn, you may cast spells as though they had flash.

This spell costs {1} less to cast for each instant and sorcery card in your graveyard.
[+1]: Create a 2/2 blue Elemental Illusion creature token with flying and “Whenever this becomes the target of a spell, sacrifice it.”
[–3]: Return up to one other target nonland permanent to its owner's hand. Draw a card.

Once during each of your turns, when a card is put into a graveyard from anywhere, you may cast it. You may spend mana of any color to cast that spell.
When Arroyo, Infinitely Branching is put into your graveyard from anywhere, you may cast it.

Flying
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)
When Bitter Corvus enters, you may reveal the top X cards of your library, where X is Bitter Corvus' power. You may put up to one card revealed this way into your hand. You lose life equal to its mana value. Put the rest into your graveyard.

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Target opponent sacrifices a creature.
Rerun (If you cast this from your hand, exile it as it resolves. Whenever a creature you control dies, you may cast this card from exile without paying its mana cost.)

When Carrion Scythe enters, if you cast it, you may return target creature card from your graveyard to the battlefield, then attach Carrion Scythe to it.
Equipped creature gets +1/+1 and has deathtouch.
Equip {2}

Deathtouch
When Corpsecaster Mage enters, if you cast it, target creature card in your graveyard gains arise until end of turn. Its arise cost is equal to its mana cost. (Exile that card from your graveyard and pay its arise cost: Create a token that's a copy of it except it's a black Zombie in addition to its other types, has no mana cost, and can't block. Arise only as a sorcery.)

Menace, haste, decayed (This can't block. When it attacks, sacrifice it at end of combat.)
At the beginning of combat on each of your turns, if you have three or more creature cards in your graveyard and haven't controlled a creature named Crypt Gnawer this turn, return Crypt Gnawer from your graveyard to the battlefield.

Search your library for a card, exile it face down, then shuffle. For as long as that card remains exiled, you may cast it. It costs {2} more to cast this way if you don't control a legendary creature as you cast that spell.

This spell costs {2} less to cast for each creature that died this turn.
Flying, trample

Casualty 1 (As you cast this spell, you may sacrifice a creature with power 1 or greater. When you do, copy this spell.)
All creatures get -2/-2 until end of turn