msem-instigator

Backstabbing Courtiers can't attack unless you foretold a card or cast a foretold spell this turn.

Target creature gets +1/+0 and can't be blocked this turn.
Showcase {2}{U} (Then if you cast this for its showcase cost, create a 1/1 red Bard creature token that can't block and exile this. Whenever it attacks, you may cast a free copy of this.)

This spell costs {U} less to cast if you dealt combat damage to a player this turn with a Rogue.
Flying
When Balloon Voyager enters, draw a card.

Counter target planeswalker spell.
Draw a card.

When Banished Prophet enters, you may remove a counter from a permanent you control. If you do, put a +1/+1 counter on another target creature you control.

Defender (This creature can't attack.)
Discard a card: Barge Engulfer can attack as though it didn't have defender until end of turn.

Vanguard — Whenever a creature you control attacks alone, it gets +1/+3 until end of turn.

Target creature you control gets +0/+3 and gains hexproof until end of turn.

{1}{U}: Target creature you control can't be blocked this turn by creatures with less power.
{1}{U}: Target creature you control can't be blocked this turn by creatures with greater power.

Flying
Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)

Creatures you control have “{T}: Add {C}.”
Mirage {1}{U} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Enchant creature
Enchanted creature gets -2/-0.
{3}{U}{U}: Submerge enchanted creature. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

When Battlemage's Disruption enters, you may return target creature to its owner's hand.
{3}{U}, Sacrifice Battlemage's Disruption: Return target creature to its owner's hand.

(Transform this if it's not attached to a creature. Pay {1}{U} as a sorcery to unattach it.)
Enchant creature you control
Bay-Bandit's Snapper's rider gets +1/+2.
Whenever Bay-Bandit's Snapper's rider deals combat damage to a player, you draw two cards.

Whenever Bazaar Informant deals combat damage to a player, reveal the top card of that player's library. If it's a nonland card, put a +1/+1 counter on Bazaar Informant, then that player puts that card into their graveyard.

If you would catalyze, catalyze twice instead. (The next spell you cast this turn costs {1} less to cast.)
You may pay an additional {2} as you cast a spell. If you do, reveal the bottom card of your library. You may put it into your graveyard or on top of your library.

When Bearer of Silk Chains enters, gain control of target nonland permanent until Bearer of Silk Chains leaves the battlefield. If that permanent is a Horror, gain control of it instead.

Look at the top two cards of your library. Put one of them into your hand, then submerge the other. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

Draw a card, then create a 1/1 blue Elemental creature token. If you drew three or more cards this turn, create three of those tokens instead.

Counter target spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Counter target spell unless its controller pays {1} or if it has the same name as a permanent or a card in a graveyard.

Enchant creature
Enchanted creature has base power and toughness 1/1 and is a Frog in addition to its other types.
When enchanted creature deals damage to a player, sacrifice Belittle.

Whenever Benevolent Host attacks, if you control another Angel or Nephilim, Benevolent Host gains flying until end of turn. Surveil 1.

When Benign Whisper enters, return another target creature to its owner's hand.

When Benthic Shipcrasher enters, scry 3.