msem-instigator

(Transform this if it's not attached to a creature. Pay {G} as a sorcery to unattach it.)
Enchant creature you control
When this permanent transforms into Packbond Mount, move all +1/+1 counters from it to its rider.
Packbond Mount's rider gets +1/+1.
{2}{G}: Put a +1/+1 counter on Packbond Mount's rider.

Sacrifice a creature: Pale Horse gets +2/+2 until end of turn.
Ride {B} ({B}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Enchant creature
Enchanted creature gets +1/+1 and has “At the beginning of each end step, you gain 1 life.”

Whenever Passionate Painter becomes untapped, you may discard a card. If you do, draw a card, then transform Passionate Painter.

Defender
Ascend {1}{W}{W} ({1}{W}{W}: Exile this creature, then return it to the battlefield transformed. Ascend only as a sorcery.)

Scry 3.
Monument {1}{U}{U} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

Choose one —
• Counter target noncreature spell.
• Peer into the Cosmos deals 3 damage to target creature.
• Until end of turn, damage that would reduce your life total to less than 1 reduces it to 1 instead.
Monument {1}{U}{R}{W} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

At the beginning of your upkeep, each player discards a card. Then if a player has no cards in hand, you may transform Performer of Ambition.

{U}, {T}: Sacrifice any number of nontoken creatures. Create an X/X blue Horror creature token, where X is the total power of those creatures. Then if X is 4 or greater, you may transform Performer of Brilliance.

{1}{R}: Performer of Desire gets +1/+1 and gains menace until end of turn. Then if its power is 4 or greater, you may transform it.

{2}, {T}: You gain life equal to the number of colors among cards in your graveyard.
{W}{U}{B}{R}{G}: Transform Performer of Enlightenment.

{T}: Add {G}. When that mana is used to cast a spell with mana value 5 or greater, you may untap Performer of Growth and transform it.

Enchant player
Whenever a creature enters the battlefield under enchanted player's control, they lose 1 life.

When Piruz, the Fourth Shah enters the battlefield, discard your hand. For each creature card discarded this way, create a 3/3 black Demon creature token with flying. For each other card discarded this way, you gain 3 life.
Monument {5}{B}{B} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

Deathtouch
Unveil {3}{B}{G} ({3}{B}{G}: Transform this. Unveil only as a sorcery.)

Vigilance, deathtouch, menace

Whenever you cast an instant or sorcery spell, each opponent loses 1 life.
Attain {3}{B} ({3}{B}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Whenever Power of Redemption attacks, choose one —
• Remove all -1/-1 counters from all creatures you control.
• Untap all creatures you control.

Prowess
Whenever Prodigal Spark is dealt damage, it deals that much damage to any target.

Flying, lifelink
Pay 5 life: Put target permanent card in a graveyard onto the battlefield under your control.

If Professor Haldean would leave the battlefield, exile him instead.
Whenever you cast a spell, you may untap Professor Haldean and another target permanent.
{T}: Professor Haldean deals 1 damage to each opponent.

Sacrifice Proud Lion: Counter target spell that targets you.
Ride {1}{W} ({1}{W}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Target player can't cast spells this turn.
Fabled {2}{W}{U} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that player.)

Vigilance

Flying, haste
Whenever Pyrus, the Undying Flame attacks, add {R}{R}{R}{R}. You don't lose this mana as steps, phases, and turns end.
{1}{R}: Pyrus gets +1/+0 until end of turn.