msem-instigator

Creatures you control that have been dealt damage this turn get +2/+0.
When Bloodspawn enters, it deals 1 damage to target creature you control.

Flying, deathtouch
When Bloodsucking Pihuchen enters, choose a nonland card name.
Whenever a permanent with the chosen name enters, each opponent loses 1 life and you gain 1 life.

Whenever Bloodthirsty Insurgent attacks, it gets +2/+0 until end of turn.

Haste
When this creature enters, exile any number of noncreature, nonland cards from your graveyard. When you do, it gets +1/+0 for each card exiled this way until end of turn.
Arise 2R ({2}{R}, Exile this from your graveyard as a sorcery: Create a black token copy of it that's also a Zombie and can't block.)

Reach
{1}{B}: Bloomcrawler gains deathtouch until end of turn.

At the beginning of your first main phase, add an amount of {G} equal to Bloomhorn's power.

Menace
Revive {1}{R} ({1}{R}, Exile this card from your graveyard: Create a token that's a copy of this card, except it has no mana cost. Activate this ability only any time you could cast a sorcery.)

When Blossom-Sower Witch enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
Whenever you sacrifice a permanent, you gain 1 life.

When Bone Lich enters, surveil 1.
{2}{B}: Return Bone Lich from your graveyard to the battlefield tapped. Activate only as a sorcery.

Whenever another creature you control dies, you may pay {1}. If you do, scry 1. (To scry 1, look at the top card of your library. You may put that card on the bottom of your library.)

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}.

{R}, {T}, Discard a card: Draw a card.
Whenever one or more cards leave your graveyard, create a Weapon token and attach it to a creature you control. (It's an Equipment artifact token with equip {2} and “Equipped creature gets +1/+1”.)

Menace (This creature can't be blocked except by two or more creatures.)
Assault {R} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)

When Braenid Nomad enters, draw two cards, then discard a card.

{1}{B}: Regenerate Brainless Ghoul. (The next time this creature would be destroyed this turn, it isn't. Instead tap it, remove all damage from it, and remove it from combat.)

Erratic (When this creature dies, reveal the top four cards of your library. Put a creature card that costs less than this revealed this way onto the battlefield and the rest on the bottom of your library in any order.)

Whenever you attack or cast a multicolored spell, put a +1/+1 counter on Brandy Axel.
If Brandy Axel would be destroyed, remove a +1/+1 counter from her. If you do, instead remove all damage from her and she deals 2 damage to each opponent.

{5}: Brass Dragon gets +3/+0 and gains flying and first strike until end of turn.

Flying

{T}: Add one mana of any color. Spend this mana only to cast an instant or sorcery spell.

Improve {1} ({1}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
When Bridgehaven's Finest enters, create a 1/1 colorless Human creature token.
Other creatures you control get +1/+1 as long as Bridgehaven's Finest has two or more counters on it.

Spells cost {1} more to cast for each colored mana symbol in their mana cost beyond the first. (For example, a spell with mana cost {W}{W} would cost {1}{W}{W} to cast.)

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.