msem-instigator

Create a 1/1 blue Bird creature token with flying. (Cast a copy of this spell once while this creature is on the battlefield.)

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

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

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.

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

Bloodfell Caves enters tapped.
When Bloodfell Caves enters, you gain 1 life.
{T}: Add {B} or {R}.

{1}, {T}, Sacrifice another creature: Put a +1/+1 counter on Bloodied Wulfhound.

Sacrifice a creature: Put a +1/+1 counter on Bloodlash Caravan. Then if it's the only creature you control, it gains indestructible until end of turn.

Target creature gets +3/+2 and gains trample until end of turn.

Blooming Vista enters tapped.
{T}: Add {R} or {G}.
{1}, {T}: Add one mana of any color.

Blossoming Sands enters tapped.
When Blossoming Sands enters, you gain 1 life.
{T}: Add {G} or {W}.

Whenever a creature dies, put a +1/+1 counter on Bog Apex.

Enchant creature
When Bogfume Pact enters, each opponent sacrifices a creature.
When enchanted creature dies, return it to its owner's hand.

Haste
Augmented — Whenever you cast a spell, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on Bolstered Guardian. It loses this ability and gains “Whenever this attacks, it deals 2 damage to each of up to two targets.”

As an additional cost to cast this spell, sacrifice a creature.
Destroy target creature.

Deathtouch

Other Hounds you control get +1/+1.

Whenever Bourasan Street Watch attacks, you may pay {W}. If you do, Bourasan Street Watch gains indestructible until end of turn.

Target opponent discards two cards. (Cast a copy of this spell once while this creature is on the battlefield.)

Gain control of target permanent. (Cast a copy of this spell once while this creature is on the battlefield.)

Create two 1/1 green Insect creature tokens. (Cast a copy of this spell once while this creature is on the battlefield.)

Whenever a creature you control becomes the target of a spell or ability, counter it unless its controller pays {1}. Whenever they do, put a +1/+1 counter on Brushcover Elf. (This includes your spells and abilities.)

Brushfire deals 3 damage to target creature. If that creature would die this turn, exile it instead.

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

You may cast this spell as though it had flash if it targets a creature or planeswalker.
Burning Up deals X damage to any target, where X is the number of basic land types among lands you control.