msem-instigator

When Benthic Shipcrasher enters the battlefield, scry 3.

Flying
Sacrifice six Swamps: Return Berbarus Unsealed from your graveyard to the battlefield with an indestructible counter on it. You draw six cards and you lose 6 life.

Trample
Bessie's Crusher has haste as long as you control another Wurm.

This spell can't be countered.
Whenever Bitter Leviathan becomes the target of a spell or ability, exile it. Return it to the battlefield under your control tapped and attacking at the beginning of the declare attackers step on your next turn. It can't be blocked that combat.

Lifelink
Whenever Bjarndyr Sergeant attacks, other creatures you control get +1/+1 and gain lifelink until end of turn.

Trample
Other Bears you control get +2/+2.

You lose 1 life and exile the top card of your library. You may repeat this process any number of times. Then put up to two cards exiled this way into your hand.
Coalesce {5}{B}{B} (You may cast this from your graveyard for its coalesce cost. If you do, put it onto the battlefield as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
Black Hole Musings's power is equal to the number of cards in exile.

Flying, lifelink
Whenever Blackhearted Sphinx attacks, you may pay 3 life. If you do, draw a card.

When Blighting Ooze enters the battlefield, put a -1/-1 counter on each of up to X target creatures.
As long as Blighting Ooze is on the battlefield, it has all activated abilities of each creature with a -1/-1 counter on it.

Flying
Blind Eternal can't be blocked by creatures with mana value 2 or less.
{3}, Discard Blind Eternal: Search your library for a noncreature card with a mana ability, reveal it, put it into your hand, then shuffle. Activate only as a sorcery.

This spell costs {1} less to cast for each creature that attacked this turn.

Trample
{T}: Add {C}.
At the beginning of your upkeep, you may pay {2}. When you do, Blundering Clocktower becomes a creature in addition to its other types until the beginning of your next end step. End the turn.

Whenever a creature dies, put a +1/+1 counter on Bog Apex.

Wither (This deals damage to creatures in the form of -1/-1 counters.)
When you unveil Bramble Quickling, you may have it fight target creature.

Double strike
{1}{R}{W}: Target creature gains double strike until end of turn. Activate only if Bravery is in your graveyard.

Haste
At the beginning of your end step, sacrifice Breach Runner unless you return another creature you control to its owner's hand.

Other creatures you control have haste.
Whenever Breach Titan enters the battlefield or attacks, abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)
At the beginning of your end step, return another target creature you control to its owner's hand.

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.)

{1}{G}: Target land you control becomes a 3/3 green Elemental creature until end of turn.
{1}{U}: Target enchantment you control becomes a 2/2 blue Nymph creature with flying until end of turn.

Flying, trample
Whenever Bretala of Redsky attacks, it gains double strike until end of turn unless defending player sacrifices a creature.

When Bridled Narwhal enters the battlefield, you gain 5 life.

Augmented — Whenever Bril, the Oltenen Emissary enters the battlefield or attacks, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, destroy target permanent.

{T}: Add {C}.
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.)

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.