msem-instigator

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

Disgraced 1 (This enters with a -1/-1 counter. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)
When Bristling Baron dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control.

Bristling Skoki has first strike as long as it's attacking.
Whenever Bristling Skoki blocks a creature, you may have it deal damage equal to its toughness to that creature.

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.

When Broadside Raider enters, create a 1/1 blue and red Pirate creature token with haste.

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.)

Bronze Giant has trample as long as you control a token creature.

Flash
Whenever you cast your second spell each turn, put a +1/+1 counter on Brooding Replacement.

Double strike
Whenever you cast a noncreature spell, you may choose one that hasn't been chosen —
• Tap or untap target permanent.
• Draw two cards, then discard a card.
• Creatures you control get +1/+1 until end of turn.

(Add a quest counter as this enters. Sacrifice after 3.)
Whenever you attack with exactly two creatures, add a quest counter.
Reveal the top four cards of your library. You may put a creature card from among them into your hand. Put the rest on the bottom in a random order.
Put two +1/+1 counters on each of up to two target creatures you control.

This spell costs {1} less to cast for each artifact and/or enchantment you control.

{6}{U}: Brume Trench-Thrasher can't be blocked this turn. This ability costs {1} less to activate for each instant and sorcery card you own in exile and in your graveyard.

Ward {2}
Whenever Brunig enters or attacks, you may shuffle a card you own from outside the game into your library. If you do, you gain 2 life.
Brunig gets +2/+2 and has trample as long as your library contains at least forty cards more than the minimum deck size.

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

Whenever a creature you control becomes the target of a spell or ability, counter it unless its controller pays {1}. Whenever they do, put a +1/+1 counter on Brushcover Elf. (This includes your spells and abilities.)

Glorious end — When Brutal Champion dies, if it was tapped, each opponent sacrifices a creature.

Flying
You may reveal the second card you draw each turn as you draw it. Whenever you reveal a nonland card this way, copy that card. You may cast the copy. If you don't, Brutal Director deals 2 damage to any target. (You still pay the spell's cost.)

Whenever one or more creatures you control deal combat damage to a player, you may destroy target artifact or enchantment that player controls.
Whenever you cast a green creature spell, create a 3/3 green Wurm creature token with trample.

Whenever another creature enters, Brutish Champion fights that creature.

Concord — Whenever Bubbledome Captain attacks, if there are four or more card types among permanents you control, each other attacking creature gets +1/+1 until end of turn.

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.'”

Whenever you cast an enchantment, instant, or sorcery spell, create a 1/1 blue Jellyfish enchantment creature token with slipstream. (It can't be blocked as long as only creatures with slipstream are attacking.)

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Concord — As long as there are four or more card types among permanents you control, Bubbledome Waveblade gets +1/+1.

When Bubblespout Sentry enters, look at the top card of your library. You may put it into your graveyard.