msem-instigator

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

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

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.

You gain 2 life. Then if you have more life than an opponent, draw a card.
At the beginning of your upkeep, if Bittersweet Reunion is in your graveyard, you may pay {1}{W} and exile it. If you do, you may copy it and cast the copy without paying its mana cost.

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 Bjarndyr Mender enters, other creatures you control get +1/+1 and gain indestructible until end of turn.

When Bjarndyr Outfitter enters, arm up to two target creatures you control. (Create a colorless Equipment artifact token with “Equipped creature gets +1/+0” and equip {2}, then attach it to that creature.)

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

Flying
When Blackblood Feaster enters, you may have each player sacrifice a creature.
Pay 2 life: Blackblood Feaster gets +2/+2 until end of turn. Activate only once each turn.

Whenever Blackfeather Cleric enters or attacks, exile target card from a graveyard. Put a +1/+1 counter on Blackfeather Cleric if it was a permanent card. Otherwise, you gain 1 life.
Surpass {5}{B} ({5}{B}: Transform this creature. This costs {1} less to activate for each counter on it. Activate only as a sorcery.)

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

At the beginning of combat on each of your turns, look at the top card of your library. You may put that card into your graveyard.
Whenever a land card is put into your graveyard from anywhere, each opponent loses 1 life and you gain 1 life.

Lifelink
{T}, Pay 4 life or sacrifice another permanent: Draw a card.

When Blackwall Ramparts enters, exile up to two target nonland permanents you don't control with total mana value 8 or less until Blackwall Ramparts leaves the battlefield.
Whenever you draw a card, you gain 1 life.

When Blackwall's Edge enters, if you control four or more lands, you may have each player conjure a card named Data-Point into their hand. (It's a sorcery that costs {2} with “Draw a card.”)
{T}: Add {C}.
When Blackwall's Edge is destroyed, return it to its owner's hand.

At the beginning of your upkeep, if Blade of Ancestors isn't attached to a creature, create a 1/1 white Soldier creature token, then attach Blade of Ancestors to it.
Equipped creature gets +1/+1.
Equip {2}

Flash
When Blade of Mautakesh enters, creatures you control gain poisonous 1 until end of turn. (Whenever those creatures deal combat damage to a player, that player gets a poison counter. Multiple instances of poisonous trigger separately.)

Double strike
Attain {3}{R} ({3}{R}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

{1}{R/W}: Untap Blade of the Long Night.

Equipped creature gets +1/+1 and has haste.
Whenever a creature you control enters, if it was cast from exile, you may attach Blade of the Valiant to it.
Equip {2}

Invigorate X, where X is the number of creatures you control. (Choose a creature with the least power among creatures you control and put X +1/+1 counters on it.)

Blazing Beam deals 4 damage to any target.

Trample, haste
When Blazing Fox enters, you may tap an untapped creature you control. If you do, Blazing Fox gets +X/+0 until end of turn, where X is that creature's power.

Blazing Offerings deals 4 damage to target creature or planeswalker.

({T}: Add {U}, {B}, or {R}.)
Bleak Dominion enters tapped.