msem-instigator

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

Target player discards a card. Return a creature card from your graveyard to your hand.

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.

When Bjarndyr Militant enters, return target Aura card or card with fabled from your graveyard to your hand.

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 {5}{B}{B}. If you do, it enters 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.

Menace
When Blackmoat Bully dies, put a +1/+1 counter and a menace counter on target creature you control.

First strike, vigilance

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.)

Flying
Whenever Blade of Reckoning deals combat damage to a player, that player sacrifices an untapped permanent.

Blade of the Many can be attached only to a nonlegendary creature.
Equipped creature gets +2/+2.
Each other creature you own is a copy of equipped creature.
Effects that would cause permanents you own to become creatures cause them to become copies of equipped creature instead.
Equip {6}

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.)

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Advance {1}{R}{W}{B} (Cast this for {1}{R}{W}{B} to advance it as it enters. {1}{R}{W}{B}: Advance this as a sorcery.)
Whenever Blastburn Angel advances, it gets +1/+1 and gains flying until end of turn. It deals 1 damage to each other creature.

Blazing Beam deals 4 damage to any target.

When Bleak Gorge Convoy enters, you may search your library for a Desert card, put it onto the battlefield tapped, then shuffle.

Enchant creature
Enchanted creature gets +2/+2.
When enchanted creature dies, return it to the battlefield under its owner's control.

Gestalt (When this or another creature you control enters, you may merge it with the one in play, keeping counters and attachments. They become the permanent on top plus all abilities from under it.)
This permanent gets +2/+2 for each card and token merged with it.

Whenever one or more creatures an opponent controls attack you or a planeswalker you control, that player gets a poison counter.

Enchant land (Target a land as you cast this. This card enters attached to that land.)
Enchanted land has “{T}: Add one mana of any color” and “At the beginning of each upkeep, untap this land.”

When Blessing of Roya enters or whenever you cast a spell from a graveyard, you gain 5 life and you mill five cards. Then you may put a card from your graveyard on the bottom of your library.

Whenever you cast an instant or sorcery spell from exile, copy it. You may choose new targets for the copy.

Creatures you control get +2/+2 until end of turn.

{T}: Add {B} or {G}.
{B}{G}, {T}: Target creature gets +1/+1 until end of turn.

Haste
When Blighted Dullahan dies, you draw a card and you lose 1 life.

Sacrifice a creature: Put a +1/+1 counter on Blightroot.
Sacrifice a land: Blightroot gains indestructible until end of turn.