msem-instigator

Prevent all damage that would be dealt to target player this turn.
Fabled {1}{W}{W}{W} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that player.)

You may activate loyalty abilities of target planeswalker you control an additional time this turn.
Fabled {1}{U}{U} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that planeswalker.)

{W}: Target creature assigns combat damage equal to its toughness rather than its power this turn.

Whenever Haunted Prodigy attacks, you may tap target creature.
Unveil {2}{W}{U} ({2}{W}{U}: Transform this. Unveil only as a sorcery.)

Whenever Haunting Maestro attacks, you may tap or untap up to two target creatures.

Deathtouch
Discard a card: Headless Carriage gains indestructible until end of turn. Tap it.
Ride {2}{B}{B} ({2}{B}{B}: Transform this and attach it to target creature you control without a Mount. Ride only as a sorcery.)

Flying, vigilance, deathtouch, lifelink

Enchant creature
When Heartstrings leaves the battlefield, exile enchanted creature.
Whenever enchanted creature attacks or blocks, exile it at end of combat.

(Transform this if it's not attached to a creature. Pay {B} as a sorcery to unattach it.)
Enchant creature you control
Herald of Death's rider gets +1/+1.
Sacrifice a creature: Herald of Death's rider gets +2/+2 until end of turn.

(Transform this if it's not attached to a creature. Pay {4}{G} as a sorcery to unattach it.)
Enchant creature you control
Herdstrider's rider gets +1/+1 for each land you control and has trample.
Whenever Herdstrider's rider attacks, create an X/X green Elephant creature token with trample that's tapped and attacking, where X is that creature's power. Exile that token at the end of combat.

Target player sacrifices any number of lands. That player searches their library for up to that many land cards, puts them onto the battlefield tapped, then shuffles.
Fabled {5}{G}{G} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that player.)

Lifelink
Tap three other untapped creatures and/or artifacts you control: Transform Heroic Crusader.

Scry 2, then create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
Monument {2}{R} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

{T}, Sacrifice Hidden Garden Entrance: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Monument {W}{U}{B}{R}{G} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

Target creature gains flying and gets +1/+0 for each card in your hand until end of turn.
Fuse (You may cast one or both halves of this card from your hand.)

Lifelink
Whenever you gain life, you may transform Hopeful Caretaker. If you don't, put a +1/+1 counter on it.

Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)
Whenever you cast an instant or sorcery spell, scry 1, then Horizon Augur gets +1/+1 until end of turn.

When Horizon Gazer enters the battlefield, reveal the top two cards of your library. Put a noncreature card revealed this way into your hand and the rest into your graveyard.
Ascend {3}{G} ({3}{G}: Exile this creature, then return it to the battlefield transformed. Ascend only as a sorcery.)

{T}: Target player exiles a card from their graveyard. If they do, you gain 1 life.

Target player creates two 1/1 white Spirit creature tokens with flying.
Fabled {3}{W}{W} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that player.)

{T}: Add {C}.
Ascend—Tap ten untapped permanents you control. (Tap ten untapped permanents you control: Exile this land, then return it to the battlefield transformed. Ascend only as a sorcery.)

When Iekin's Portal enters the battlefield, look at the top five cards of your library. Put one into your hand and the rest into your graveyard.
{1}{U}{U}: Transform Iekin's Portal. Activate only if your fealty to Islands is five or greater.

Indestructible
You have no maximum hand size.
Whenever an opponent draws a card, you draw a card.
If you would lose the game other than for having 0 or less life, you win the game instead. (Another player winning the game does not cause you to lose the game.)

Flying
Whenever Immaculate Clouddasher attacks, up to three target creatures gain flying until end of turn.

Enchant creature
Enchanted creature gets +3/+3 and has flying.