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.)

Flash
Flying
When Branu enters, return up to one other target creature you control to its owner's hand. If you do, create a token that's a copy of that creature, except it's 1/1.

Flash
When this creature enters, surveil 1, then draw a card.

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.)

Whenever this creature or another creature you control dies, this creature deals 1 damage to each opponent.

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.

When Briarswine dies, create a 2/2 green Wolf creature token.
Foreshadow {4}{G} (You may cast this spell for its foreshadow cost. If you do, also trigger its “dies” abilities when it enters.)

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.

{2}{R}, Sacrifice a creature: Target creature can't block this turn.

Invocation — Whenever you spend four or more mana to cast a spell or activate an ability during your turn, Brine Cultist can't be blocked this turn.
{5}{U}: 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.)