msem-instigator

(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 you cast an instant or sorcery spell, each opponent loses 1 life and Beast of Pestilence gets +1/+1 until end of turn.

Whenever Beatrice's Dodger attacks, create a 1/1 black and red Human Rogue creature token that's tapped and attacking.
{3}{B}{R}: Return Beatrice's Dodger from your graveyard to the battlefield
tapped and transformed.

X target creatures can't block this turn.
Fuse (You may cast one or both halves of this card from your hand.)

(Transform this if it's not attached to a creature. Pay {2}{B}{B} as a sorcery to unattach it.)
Enchant creature you control
Belmord Blood-Coach's rider gets +3/+3 and has deathtouch.
Whenever Belmord Blood-Coach's rider attacks, you may return target creature card with mana value less than its rider's power from your graveyard to the battlefield tapped.

Prevent all combat damage that would be dealt to and dealt by Bereaved Aristocrat.
Unveil {2}{W}{U} ({2}{W}{U}: Transform this. Unveil only as a sorcery.)

Enchant creature
At the beginning of the upkeep of enchanted creature's controller, Betrayer's Mantle deals 3 damage to that player.

Exile target card from a graveyard. Create a 1/1 black Worm creature token.
Fuse (You may cast one or both halves of this card from your hand.)

Create two tapped colorless land tokens named Far-Off Lands with “{T}: Add one mana of any color.” (Then exile this card. You may cast the creature later from exile.)

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

Legacy (You may play this side of this card only from your graveyard. Exile it if it would leave the battlefield or not resolve.)
Permanents you control have lifelink and “{T}: Add one mana of any color.”

At the beginning of your end step, mill two cards. Then if ten or more cards are in your graveyard, transform Bitter Duckling.

Whenever Blackfeather Cleric enters or attacks, exile target card from a graveyard. Put a +1/+1 counter on Blackfeather Cleric if it was a permanent card. Otherwise, you gain 1 life.
Surpass {5}{B} ({5}{B}: Transform this creature. This costs {1} less to activate for each counter on it. Activate only as a sorcery.)

At the beginning of your upkeep, if Blade of Ancestors isn't attached to a creature, create a 1/1 white Soldier creature token, then attach Blade of Ancestors to it.
Equipped creature gets +1/+1.
Equip {2}

Double strike
Attain {3}{R} ({3}{R}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Exile target instant or sorcery card from your graveyard. Copy it. You may cast the copy. (Cast a copy of this spell once while this creature is on the battlefield.)

Bleakrealm Moor enters tapped unless you played it from exile.
{T}: Add {B} or {R}.

Enchant land
Whenever enchanted land is tapped for mana, its controller adds two mana in any combination of colors (in addition to the mana the land produces.)

Vigilance
Blessed Suncrusher's power and toughness are each equal to your life total.

Put a +1/+1 counter on target creature you control.
Monument {1}{G} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

Blighted Unicorn can't block.
Ride {3}{B} ({3}{B}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

When Blinding Fiddler enters, until your next turn, creatures can't attack you or a planeswalker you control unless their controller pays {2} for each of those creatures.
Unveil {3}{W}{U} ({3}{W}{U}: Transform this. Unveil only as a sorcery.)

Whenever Blood Constrictor becomes blocked by a creature, you gain life equal to that creature's toughness.

Destroy target creature that was dealt damage this turn. (Then exile this card. You may cast the creature later from exile.)

Flying, menace
Sacrifice a creature: Put two +1/+1 counters on Bloodclaw Demon. It gains indestructible until end of turn.