msem-instigator

First strike
Whenever you cast an instant or sorcery spell, if Branch Breaker dealt combat damage to a player this turn, you may sacrifice Branch Breaker. If you do, copy that spell. You may choose new targets for the copy.

Branch Prowler can't be blocked except by creatures with flying.

Erratic (When this creature dies, reveal the top four cards of your library. Put a creature card that costs less than this revealed this way onto the battlefield and the rest on the bottom of your library in any order.)

When Brawlhost Escapee dies, create a Function token with “Target creature you control fights target creature you don't control.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Haste
Whenever one or more creatures attack, you may discard a card. If you do, draw a card.

Breezerider has flying as long as you control a Nymph.
Breezerider has hexproof as long as you control another Monkey.

When Briarform Apothecary enters, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
Sacrifice a token: Briarform Apothecary gets +2/+2 until end of turn.

Lifelink
When Bright-Eyed Adventurer enters, rediscover an enchantment card. (Look at the top card of your library. You may reveal it and put it into your hand if it's an enchantment card. Otherwise, put it back or into your graveyard.)

Flash
When Brightsouled Guardian enters, return up to one target nonland permanent to its owner's hand.

Prowess, trample
Whenever Brilliant Diviner deals combat damage to a player, draw a card.

Whenever you draw a card, you may have target player mill two cards.

Whenever Bristled Wolverine attacks, it gets +1/+1 until end of turn.

Broken Deathbringer gets +1/+0 as long as you have 10 or less life.
Broken Deathbringer gets +1/+0 as long as there are one or fewer cards in your hand.

When Broken Spirit enters, exile target creature an opponent controls until Broken Spirit leaves the battlefield.
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.)

Reach
Hexproof (This creature can't be the target of spells or abilities your opponents control.)

When Bubbledome Chorister enters, create a green Aura enchantment token named Sanctum's Gift attached to target creature. The token has enchant creature and “Enchanted creature has ‘{T}: Add {G} for each enchanted creature you control.'”

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
When Budding Companion has three or more +1/+1 counters on it, remove them all and transform it.

{T}, Sacrifice a creature: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
{T}, Sacrifice a Clue: Create a 3/3 green Elemental creature token.

Haste
{T}: Discard a card, then draw a card.
Paranoia {2}{R} (You may cast this spell for its paranoia cost when a permanent you control leaves the battlefield.)

Whenever Burning Hart deals combat damage to a player, it deals that much damage to up to one target planeswalker that player controls.

Flying
Whenever Buzzing Flitter attacks, you may pay {G}. If you do, untap target permanent.

When Byron, Unlikely Hero enters, put a +1/+1 counter on each other Citizen or Peasant you control.
Whenever a nontoken creature you control with a +1/+1 counter on it dies, create a 1/1 white Peasant creature token.

Flying
Whenever you gain life, each opponent loses 1 life.

Haste
Revive {3}{R} ({3}{R}, Exile this card from your graveyard: Create a token that's a copy of this card, except it has no mana cost. Activate this ability only any time you could cast a sorcery.)

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Whenever a marked creature you don't control blocks, Cadalon Chemist deals 1 damage to that creature.