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.

Surveil 1, then draw a card. (To surveil 1, look at the top card of your library. You may put that card into your graveyard.)
Create a tapped Treasure token.

Whenever you draw a card, put a loyalty counter on Tara, Duneblessed.
[–1]: Create a 1/1 white Soldier creature token. Investigate.
[–2]: If target artifact or creature is tapped, exile it. Otherwise, tap it and put a stun counter on it.
[–10]: Choose up to one creature. Destroy the rest.

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever Mindscreech Drake deals combat damage to a player, that player mills three cards.

Haste
Sacrifice a land: Trail Blazer explores. You may put a basic land card from your hand onto the battlefield tapped. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then you may put that card in your graveyard.)

Defender (This creature can't attack.)
{W}, {T}: You gain 1 life.

Enspirit (As you cast this spell, you may exile a nonenchantment creature you control until this leaves the battlefield or fails to resolve. Reduce this spell's cost by the exiled card's mana value.)
Trample

{1}, Sacrifice Sovereign Stone: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
{1}, Sacrifice Sovereign Stone: Draw a card.

Whenever a source you control deals noncombat damage to a player, put a +1/+1 counter on Mindblaze Pyromancer.

End the turn. If it's an opponent's turn, they take an extra turn after this one. (Exile all spells and abilities from the stack, including this card. The player whose turn it is discards down to their maximum hand size. Damage wears off, and “this turn” and “until end of turn” effects end.)

[+1]: Mpumo, Who Stands Alone deals 1 damage to any target and you gain 1 life.
[–X]: Exile target creature with mana value X.
[–6]: Choose up to four permanents an opponent controls. That player chooses one, then sacrifices the rest.

Abandoned Hideout enters tapped if you control another nonbasic land.
{T}: Add {U} or {R}.

Creatures you control get -3/-3.
Whenever a creature you control dies, put a soul counter on Remake the Cast.
Creatures you control get +1/+1 for each soul counter on Remake the Cast.

At the beginning of combat on your turn, you may have Regurgitator Ooze consume. If you do, it gets +2/+2 until end of turn. (To consume, sacrifice another creature or exile a creature card from your graveyard.)
When Regurgitator Ooze dies, return a card exiled with it to its owner's hand.

When Goblin Sniper dies, you may pay {R}. If you do, it deals 2 damage to target opponent or planeswalker.

Flying
When Sky-Torrent Navigator enters, forebode. If you control two or more Pirates, forebode again. (To forebode, create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

{T}: Exile two target creature and/or land cards from a graveyard. Create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
{B}{G}, Sacrifice two Vials: Sacrifice Leticia Petrine, then return her to the battlefield transformed under her owner's control.

Flash
Flying
When this creature enters, you gain 3 life.

Deathtouch
{U/B}: Change a target of target spell or ability that targets Serafina to another creature you control.
Whenever Serafina deals damage to a player, at the beginning of the next end step, that player loses life equal to the life they lost this turn.

Enchant creature
As Legacy of Siltbottom enters, choose a creature type.
Enchanted creature gets +3/+3 and is the chosen type in addition to its other types.

Archive 2 (As this enters, shuffle the top two cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
{R}{W}: Put a nontoken artifact or creature you own on the bottom of the archived library. Create a token that's a copy of it.

Flying
Your opponents lose the game if their life total is less than or equal to the total number of cards you own in exile and in your graveyard that have flashback rather than 0 or less.

Vigilance
When Inquisitive Student enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

For each permanent type, return up to one target card of that type from your graveyard to your hand. (The permanent types are artifact, creature, enchantment, land, and planeswalker.)

Trample, haste
Cadence (Whenever you cast a spell, if its mana value is greater than this creature's power, put a +1/+1 counter on this creature.)