msem-instigator

This spell costs {1} less to cast if it targets an attacking creature.
Target creature gets +2/+0 and gains indestructible until end of turn.

Flying, vigilance
Whenever one or more other creatures you control attack, those creatures get +0/+2 until end of turn.
Whenever one or more other creatures you control block, those creatures get +2/+0 until end of turn.

Menace
At the beginning of your end step, if you lost 4 or more life this turn, you may create Irgh'vall, a legendary 4/4 black Demon creature token with flying.

Vanguard's Assault deals X damage divided as you choose among any number of target creatures, where X is the number of attacking creatures.

Whenever you play a land, you may search your library for a land card that shares a subtype with it, put it onto the battlefield tapped, then shuffle.

Bloodcrazed Acolyte enters with a +1/+1 counter on it for each player who lost life this turn.

{3}{W}: Return another target artifact or creature you control to its owner's hand.
{1}{B}: Surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)

{R}: Draconic Aspirant gets +1/-1 until end of turn.

Resolute — At the beginning of combat on your turn, if Glisterhorn's power is greater than its base power, tap target creature an opponent controls.

Flying, hexproof
At the beginning of your end step, put an exiled card with an ancestry counter on it on the bottom of its owner's library, then scry 2. If there is exactly one card exiled with an ancestry counter on it, transform Atieh.

[+1]: Create a 1/1 white Cat creature token with lifelink.
[–1]: When you next activate a nonmana ability of target permanent this turn, copy that ability. You may choose new targets for the copy.
[–7]: Exile up to seven target permanents. Return those cards to the battlefield under their owner's control at the beginning of the next end step.

Whenever equipped creature blocks or becomes blocked by a creature, you may have equipped creature become a copy of that creature until end of turn.
Equip {1}

Vision (Whenever this or another creature you control enters, reveal the top card of your library. Then you may put that card into your graveyard.)
Whenever Spectral Hunter envisions a creature card, creatures you control get +1/+0 until end of turn.

Defender

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

Deception {1}{B} ({1}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Unblocked attacking creatures you control get +1/+0.

Whenever one or more creatures you control deal combat damage to a player, that player discards a card. Then that player may discard another card. If they don't, create two 2/1 black Nightmare creature tokens with “This creature can't block.”
Fleeting {1}{B}{B} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

When Cyone, Expedition Captain enters, create a 1/1 Scout creature token that's all colors, then choose flying, first strike, or lifelink. Creature tokens you control gain the chosen ability until end of turn.
Whenever Cyone attacks, aetherize it. (To aetherize, create a token that's a copy of it, then exile that token.)

{T}, Sacrifice Decrepit Crags: Search your library for a Swamp or Mountain card and put it onto the battlefield tapped, then shuffle.

When Fading Prison enters, exile target creature until Fading Prison leaves the battlefield.
{W}, Sacrifice Fading Prison: Exile target creature you control, then return that card to the battlefield under its owner's control.

When Rat King enters, create two 1/1 black Rat creature tokens with “This creature can't block.”
Whenever Rat King or another creature you control dies, each opponent loses 1 life and you gain 1 life.

{T}: The next time you would draw a card this turn, instead search your library for a card, put it into your hand, then shuffle. Activate only as a sorcery.

{W}, {T}: Tap target creature.

When Rune-Scribe's Apprentice enters, target player mills four cards.

An opponent separates all noncreature, nonland cards in your graveyard into two piles. Put one pile into your hand and exile the other. Exile Conflicting Records.