msem-instigator

Menace, haste
At the beginning of combat on your turn, gain control of up to two target noncreature, nonland permanents your opponents control until end of turn. Untap those permanents. You may attach any number of Equipment among them to creatures you control until end of turn. (They unattach at end of turn.)

This spell can't be countered.
Hexproof

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
During each of your turns, you may cast an instant or sorcery spell from your graveyard. If that spell would be put into your graveyard, exile it instead.
Whenever Aurora, Soulweaver attacks, untap any number of target creatures.

Once each turn, when you cast a noncreature spell, create a 1/1 colorless Human creature token. Put a prowess counter on it.

When Autumnal Resonants enters, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Create a 3/3 red and green Elemental creature token with haste.

Trample
Harmony — Avalanche Drummer deals 1 damage to any target.
When Avalanche Drummer enters, harmonize. (Trigger up to one harmony of a permanent you control.)

Frenzy 2 (Whenever this creature attacks and isn't blocked, it gets +2/+0 until end of turn.)
Blocked creatures you control have first strike.

Menace (This creature can't be blocked except by two or more creatures.)
Avatar of Basat can't block.

First strike
When Avaz Cataphract enters, judge another target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

Flying
When Aven Strategist enters, return up to one target creature to its owner's hand.

Trample
Whenever a player casts a noncreature spell, that player sacrifices a noncreature permanent.

You may exert Awoken Elemental as it attacks. When you do, Awoken Elemental fights another target creature. (An exerted creature won't untap during your next untap step.)

When Azure Archaeologist enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
{2}, {T}, Sacrifice a Clue: Draw two cards, then discard a card.

Flying, trample
Prismatic — Whenever you cast a multicolored spell, put a +1/+1 counter on Azure Caterwauler.

Desecrate (When this creature enters, you may sacrifice an artifact or land.)
When Back-Alley Vandal desecrates a permanent, put a +1/+1 counter on Back-Alley Vandal.

Haste
When Backdrop Artisan dies, audition for red. (Create a 1/1 Construct Actor creature token, a Warrior Role giving 3/2 and trample, or a Wizard Role giving 2/2 and prowess. Roles replace older ones.)

When Backstage Broken enters, create a 1/1 colorless Construct Actor creature token.
Whenever a token you control leaves the battlefield, you gain 1 life.

Whenever Backstreet Gutter-Runner attacks, if you control another Pirate or Rogue, it deals 2 damage to each opponent.

Whenever you create one or more tokens, put a +1/+1 counter on target creature you control.
{2}{G}{W}: Create a 0/1 green Plant creature token.

Prowess
Whenever Balefire Conjurer attacks, you may pay {1}{R}. If you do, exile the top card of your library. You may play that card until the end of your next turn.

Menace
As long as Balefire Harbinger is attacking, creatures in its pack can't be blocked unless defending player pays {1} and 1 life for each creature they control that's blocking one of those creatures. (Two or more creatures you control with equal power are in a pack.)

Haste (This creature can attack and {T} as soon as it comes under your control.)
{1}{U}: Balloon Dragoon gains flying until end of turn.

When Banished Prophet enters, you may remove a counter from a permanent you control. If you do, put a +1/+1 counter on another target creature you control.

When Banishing Initiate enters, you may exile target nonland permanent you don't control until Banishing Initiate leaves the battlefield.
At the beginning of your end step, sacrifice Banishing Initiate if a card exiled with it has mana value 3 or greater.

When Barbarian Hoarders enters, you may attach target Equipment you control to it.