msem-instigator

When Bind the Mind enters, each poisoned opponent reveals their hand. Then choose a nonland card name.
Spells with the chosen name can't be cast.

Enchant creature
Enchanted creature can't attack or block alone.

Equipped creature gets +1/+1.
Whenever equipped creature becomes blocked, you may pay {1}{W}. If you do, detain each creature blocking it. (Until your next turn, those creatures can't attack or block and its activated abilities can't be activated.)
Equip {2}

Flash
When Binding Stones enters, exile target creature with power 3 or less until Binding Stones leaves the battlefield.

When Bio-Sequencer enters, conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)
{1}, {T}, Sacrifice Bio-Sequencer: Add one mana of any color.

{T}: Add one mana of any color a basic land you control could produce.

Enchant creature
Enchanted creature gets +2/+2 and has lifelink.

When Biohazard enters, destroy all other nonland permanents with mana value X or less.
At the beginning of each end step, each opponent loses life equal to the number of cards they've drawn this turn plus the number of spells they've cast this turn.

When Bioluminescent Predator dies, draw a card, then you may put a land card from your hand onto the battlefield.

When Bird Call enters, search your library for a creature card, reveal it, shuffle, then put that card on top.
{2}, {T}: Target creature gets +1/+1 until end of turn.

Lifelink
At the beginning of your end step, if you've gained 3 or more life this turn, create a 2/2 white Bird creature token with flying.

Flying
Bird of Many Feathers can block only creatures with flying.
Whenever you scry, put a +1/+1 counter on Bird of Many Feathers.

Legacy (You may play this side of this card only from your graveyard. Exile it if it would leave the battlefield or not resolve.)
Permanents you control have lifelink and “{T}: Add one mana of any color.”

Whenever a creature card is put into your graveyard from the battlefield, exile it. You lose life equal to that card's mana value. Put it onto the battlefield tapped at the beginning of your next upkeep.

Whenever Birthing Elemental or another nontoken creature you control dies, create a 1/1 green Saproling creature token.

Menace
When Bit Player dies, it deals 1 damage to each opponent.

At the beginning of your end step, mill two cards. Then if ten or more cards are in your graveyard, transform Bitter Duckling.

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.

When Bitter Pact enters, destroy target nonbasic permanent.
All permanents and players lose hexproof, indestructible, and protection and can't have or gain hexproof, indestructible, or protection.

Whenever you put one or more -1/-1 counters on a creature, create that many 1/1 black Faerie creature tokens with flying.

Desecrate (When this creature enters, you may sacrifice an artifact or land.)
When Bitter Wanderer desecrates a permanent, each opponent loses 2 life and you gain 2 life.

Deathtouch
When Bitterheart Bokor leaves the battlefield, you may search your library for a Curse card, reveal it, put it into your hand, then shuffle.

At the beginning of your upkeep, exile the top card of your library. If a land card is exiled this way, add {R}{R}. You don't lose this mana as steps and phases end this turn. Otherwise, you may cast that card this turn.

When Bizarre Dreams enters, destroy up to one target artifact or enchantment.
{3}{W}, Sacrifice Bizarre Dreams: Create two 1/1 blue Elemental creature tokens with flying. They can't block this turn.

Bjarndyr Bruiser gets +2/+2 as long as it's embattled. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)