msem-instigator

Target creature gets -4/-4 until end of turn. If that creature would die this turn, exile it instead.
Cycling {2} ({2}, Discard this card: Draw a card.)

Whenever you discard a card or an artifact is put into your graveyard from the battlefield, put a +1/+1 counter on Bloodhollow Bruiser.
Cycling {2} ({2}, Discard this card: Draw a card.)

Target creature gets +1/+0 and gains first strike until end of turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

Menace (This creature can't be blocked except by two or more creatures.)
Cycling {R} ({R}, Discard this card: Draw a card.)

Create three 1/1 blue and red Pirate creature tokens with haste.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Sacrifice Bonetooth Darter: Counter target instant, planeswalker, or sorcery spell unless its controller pays {1}.

Enchant creature
When Bramble Armor enters, put a +1/+1 counter on enchanted creature.
{G}, Sacrifice Bramble Armor: Enchanted creature gains indestructible end of turn. Tap it.

You may put a permanent card from your hand onto the battlefield. If it's a planeswalker, it enters with five loyalty counters rather than any other amount, and you may activate its loyalty abilities this turn any time you could cast an instant.

Whenever Breakneck Barque becomes blocked by a creature, Breakneck Barque deals 3 damage to that creature.
Crew 3 (Tap any number of creatures you control with total power 3 or greater: This Vehicle becomes an artifact creature until end of turn.)

When Bridled Narwhal enters, you gain 5 life.

Deathtouch
When Brig of the Damned enters, return target creature card from your graveyard to your hand. If that card's mana value is 2, you may return it to the battlefield instead.
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

Brilliant Runepearl enters tapped.
Whenever you cast a permanent spell, you gain 1 life.
{T}: Add one mana of any color. Spend this mana only to cast permanent spells.

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.

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

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

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.

Pressure {B} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
Search your library for a card, put it into your graveyard, then shuffle. You gain 2 life.

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

Target creature gets +4/+2 and gains trample until end of turn.

Permanents you control with mana value 1 or less have first strike, haste, and lifelink.

Whenever Bygone Wreck deals combat damage to a player, you may sacrifice it. If you do, create five Treasure tokens.
Crew 1 (Tap any number of creatures you control with total power 1 or greater: This Vehicle becomes an artifact creature until end of turn.)