msem-instigator

Whenever a creature you control deals combat damage to a player, you may sacrifice it. If you do, draw cards equal to that creature's power.

Whenever Bound Apparition becomes the target of a spell or ability, put a -1/-1 counter on it.

Flying
When Boundless Hopes enters, another target creature you control gains flying until end of turn.
Fleeting {U} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.

{1}, Sacrifice Brackwater Scuttler: Draw a card.

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

Counter target spell. Spells its controller casts cost {2} more to cast this turn.

Braineater Abominus can't be blocked by creatures with power 4 or greater.
Whenever a creature you control deals combat damage to a player, exile the top card of that player's library. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any type to cast it.

If you would draw a card, instead exile the top three cards of your library face down. You may look at those cards. Put a card exiled with Brainstorming Session into its owner's hand.
{X}{X}{U}, Sacrifice Brainstorming Session: Put X cards exiled with it into their owner's hand.

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

Flash
When this creature enters, surveil 1, then draw a card.

Flying

Breezerider has flying as long as you control a Nymph.
Breezerider has hexproof as long as you control another Monkey.

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

Flying
Whenever you cast a spell from anywhere other than your hand, Brightwing Sphinx gains vigilance until end of turn.

Tap up to four target nonland permanents. Nonland permanents your opponents control don't untap during their controller's next untap step.

Invocation — Whenever you spend four or more mana to cast a spell or activate an ability during your turn, Brine Cultist can't be blocked this turn.
{5}{U}: Draw a card.

Whenever Brine Kelpie attacks, you may tap target creature an opponent controls.
Ride {2}{U} ({2}{U}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Whenever you draw a card, you may have target player mill two cards.

This spell costs {1} less to cast for each artifact and/or enchantment you control.

{6}{U}: Brume Trench-Thrasher can't be blocked this turn. This ability costs {1} less to activate for each instant and sorcery card you own in exile and in your graveyard.

Target creature gets +0/+3 until end of turn. Whenever that creature perseveres this turn, draw a card. (A creature perseveres when it survives damage.)

Whenever you cast an enchantment, instant, or sorcery spell, create a 1/1 blue Jellyfish enchantment creature token with slipstream. (It can't be blocked as long as only creatures with slipstream are attacking.)

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Concord — As long as there are four or more card types among permanents you control, Bubbledome Waveblade gets +1/+1.