msem-instigator

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Flying
Other creatures you control with flying get +1/+1.

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.

Flying, double strike
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

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.

Sacrifice a creature: Exile the top card of your library. Until end of turn, you may play that card.

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.)

Eureka! (At the beginning of each end step, you get a research counter if you cast a spell this turn. Then if you have eight or more research counters, remove them and create a Masterpiece token of your choice.)
{T}: Draw a card, then discard a card.

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

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.

Deathtouch
When Backstage Comic enters, target player discards a card.

Lifelink
Whenever Backstage Prompter deals combat damage to a player, put a +1/+1 counter on it.

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

When Backwoods Cultivator enters, put a +1/+1 counter on target creature you control.
When Backwoods Cultivator dies, proliferate. (You choose any number of permanents and/or players with counters on them, then give each another kind of a counter already there.)

Deathtouch
Bahet's Emissary gets +1/+1 as long as you control a white or black permanent.

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.

Double strike
Engage (This creature must be blocked each combat if able.)
{1}{R}: Balanced Blade gets +1/+0 until end of turn.

Flying, deathtouch

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 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.

Trample
When Bank Skimmer enters, create a green Aura enchantment token named Turtle's Valor attached to target creature. The token has enchant creature and “Enchanted creature gets +X/+X, where X is its mana value.”

Battalion — Whenever Barbarian Rager and at least two other creatures attack, Barbarian Rager gets +2/+0 until end of turn.