msem-instigator

Choose one—
• Manifest target creature card from your graveyard. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)
• Return up to two target creature cards from your graveyard to your hand.

{G}, {T}, Remove a +1/+1 counter from a creature you control: Create a 2/2 green Ox creature token.

Whenever Borsuppa Roughrider attacks, create a colorless Desert land token named Scoured Path with “{T}: Add {R}.” Sacrifice that token at the beginning of the next end step.

You may cast a spell with mana value 3 or less from your hand without paying its mana cost. (Then exile this card. You may cast the creature later from exile.)

Whenever a creature with a counter on it dies, create a Gold token. (It's an artifact with “Sacrifice this artifact: Add one mana of any color.”)

Harmony — Create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”
When Bouquet Singer enters, harmonize. (Trigger up to one harmony of one permanent you control.)

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 player discards two cards.
Fabled {3}{B}{B} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that player.)

Wither (This deals damage to creatures in the form of -1/-1 counters.)
When you unveil Bramble Quickling, you may have it fight target creature.

When you cast this spell, copy it. You may choose new targets for the copy. (Copies keep functions.)
Draw a card.

Disgraced 2 (This enters with two -1/-1 counters. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)
When Branded Contractor dies, you may put its counters on target creature.

Whenever a creature you control deals combat damage to a player or planeswalker, you may pay {W} and/or {U}. When you pay {W} this way, put a +1/+1 counter on target creature you control. When you pay {U} this way, draw a card.

When Brawlhost Escapee dies, create a Function token with “Target creature you control fights target creature you don't control.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Enchant creature you control
When Brawnsurge enters, enchanted creature deals damage equal to its power to up to one target creature an opponent controls.
Enchanted creature gets +1/+1 and has trample.

Alpha (You may have this creature enter with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)
Brazen Chimera can't be blocked except by three or more creatures as long as it has a +1/+1 counter on it.

Haste
Whenever one or more creatures attack, you may discard a card. If you do, draw a card.

Haste
At the beginning of your end step, sacrifice Breach Runner unless you return another creature you control to its owner's hand.

Counter target spell unless its controller discards two cards.

Until end of turn, target creature gets +2/+2 and gains trample and “Whenever this creature deals combat damage to a player, investigate.” (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Whenever Breakneck Barque becomes blocked by a creature, Breakneck Barque deals 3 damage to that creature.
Crew 3 (Tap any number of creatures you control with total power 3 or greater: This Vehicle becomes an artifact creature until end of turn.)

{1}{G}: Target land you control becomes a 3/3 green Elemental creature until end of turn.
{1}{U}: Target enchantment you control becomes a 2/2 blue Nymph creature with flying until end of turn.

When Briarform Apothecary enters, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
Sacrifice a token: Briarform Apothecary gets +2/+2 until end of turn.

Hexproof
Whenever attackers are declared, the active player may pay {2} for each creature attacking you. Then you may have Bridge Kalak become an X/X Troll creature until end of turn, where X is the number of times that player didn't pay mana this way.

Flash
When Brightsouled Guardian enters, return up to one target nonland permanent to its owner's hand.