msem-instigator

Defender
When Brine Duelist enters, create a Treasure token. (It's an artifact with “{T}, Sacrifice this permanent: Add one mana of any color.”)
{W}{U}{B}{R}{G}: Put a +1/+1 counter on Brine Duelist. It loses defender.

Whenever Brine Kelpie attacks, you may tap target creature an opponent controls.
Ride {2}{U} ({2}{U}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Destroy target creature with flying.
Draw a card.

Target creature gets +3/+0 until end of turn. Mill three cards.

Trample
When Bringer of Armies enters, recruit. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)

Flying, vigilance
Protection from Humans (This creature can't be blocked, targeted or dealt damage by Humans.)

At the beginning of your upkeep, you may discard a land card. When you do, create a 2/2 green Wolf creature token.

Target player draws seven cards, then their life total becomes equal to the number of cards in their hand.

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.

Distribute three +1/+1 counters among up to three target creatures you control. Those creatures gain first strike until end of turn.

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.

Create two 1/1 green Insect creature tokens. (Cast a copy of this spell once while this creature is on the battlefield.)

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.

Target creature gets +0/+3 until end of turn. Whenever that creature perseveres this turn, draw a card. (A creature perseveres when it survives damage.)