msem-instigator

When Blighting Ooze enters, 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.

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

Flash
Blind Blackguard can't block.
When Blind Blackguard enters, target player draws a card, then reveals their hand. You choose a nonland card from that player's hand, then that player puts the chosen card on the bottom of their library.

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.

Breach (Whenever this deals combat damage to a player, you may have it become an Aura Curse until your next turn. Attach it to that player.)
At the beginning of your end step, each cursed opponent loses 2 life unless they discard a card.

Renown 2 (When this creature deals combat damage to a player, if it isn't renowned, put two +1/+1 counters on it and it becomes renowned.)
When Blind Sharpshooter becomes renowned, it deals 2 damage to target creature defending player controls.

Vision (Whenever this or another creature you control enters, reveal the top card of your library. Then you may put that card into your graveyard.)
Whenever Blind Soulcaller envisions an instant or sorcery card, you may tap target permanent.

Prowess

{4}{R}: Blind Tunneler gets +3/+0 until end of turn.

Flying
Glorious end — When Blinded Avenger dies, if it was tapped, destroy target creature you don't control.

Lifelink
Revive {3}{B} ({3}{B}, 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.)

Enchant creature
Enchanted creature gets +1/+1 and has hexproof.

When Blisterbug dies, put two +1/+1 counters on target creature you control.

{T}: Add {C}.
Dominance — {1}, {T}: Blistering Boneyard deals 1 damage to each opponent. Activate only if you control the creature with the greatest power or tied for the greatest power.

Advance {1}{R} (Cast this for {1}{R} to advance it as it enters. {1}{R}: Advance this as a sorcery.)
Whenever Blitz Breaker advances, its power becomes equal to the amount of noncombat damage that's been dealt to your opponents this turn. (This effect lasts indefinitely.)

Flying
Whenever Blizzard Dragon attacks, tap an artifact, a creature, and a land defending player controls. They don't untap during their controller's next untap step.
At the beginning of each opponent's upkeep, that player sacrifices a tapped permanent.

Target player discards two cards.
Orchestrate {1}{B}{B} (You may exile this card from your hand anytime you could cast a sorcery for its orchestrate cost. When you next resolve a spell, you may cast this from exile without paying its mana cost.)

Cycling {2} ({2}, Discard this card: Draw a card.)
{3}{B}{B}, Exile Bloated Visceroid from your graveyard: Create two 2/2 black Zombie creature tokens. Activate only as a sorcery.

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Sacrifice another creature: Blood Bairn gets +2/+2 until end of turn.

Whenever an attacking creature you or a teammate controls dies, you lose 1 life and draw a card.

At the beginning of each end step, if an opponent lost life this turn, you may put a +1/+1 counter on target creature.
Sacrifice a creature, Sacrifice Blood Cult Covenant: Blood Cult Covenant deals damage equal to the sacrificed creature's power to any target.

Menace (This creature can't be blocked except by two or more creatures.)
Blood Fiend can't block.
{1}{B}, Pay 3 life: Return Blood Fiend from your graveyard to the battlefield. It gains haste.

Target creature gets +3/-3 until end of turn.
Kindle 3—{B}{R}, Pay 3 life. ({B}{R}, Pay 3 life, Exile this card from your graveyard: Create three 1/1 colorless Elemental creature tokens. Kindle only as a sorcery.)

Nonbasic lands have “Whenever this land becomes tapped, you lose 1 life unless you sacrifice this land.”