msem-instigator

Enchant creature
Enchanted creature gets +2/+2 as long as it's legendary. Otherwise, it can't attack or block.
When enchanted creature dies, if it's legendary, return that card to its owner's hand.

Enchant creature
Enchanted creature has flying.
{2}: Tap enchanted creature.

Whenever West Ward Purifier becomes tapped, you gain 1 life.

You gain 5 life and draw a card. Then if you've cast spells named When the Stars Align five times this game, you win the game.
Augmented — If you've spent {W}{U}{B}{R}{G} to cast spells this turn, you may shuffle When the Stars Align into your library.

Flying, lifelink
Creatures entering or leaving the battlefield don't cause abilities to trigger unless that creature is in a pack. (Two or more creatures a player controls with equal power are in a pack.)

Enchant creature
Enchanted creature can't attack or block.
{2}{U}: Return Whiplash and enchanted creature to their owners' hands.

Create a 1/1 white Spirit creature token with flying.
Whenever a nontoken creature you control dies, you may pay {W} and exile Whispered Wishes from your graveyard. If you do, create a 1/1 white Spirit creature token with flying.

Double strike

Vigilance

Alpha (You may have this creature enter the battlefield with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)

When Whiterun Ordainer enters the battlefield, you gain 4 life.

Flying (This creature can't be blocked except by creatures with flying or reach.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

When Wilderness Forager enters the battlefield, you may reappropriate. If you do, gain 6 life. Otherwise, gain 3 life. (To reappropriate, exile exactly two cards from your hand and/or graveyard.)

Create two 1/1 colorless Samurai creature token. Those creatures gain first strike until end of turn.

Create a 1/1 green and white Mouse Soldier creature token with vigilance and a 1/1 white and black Badger Cleric creature token with lifelink.

Flying
Whenever Wind Savant attacks, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Wind Savant gets +1/+1 until end of turn.

Flying
Windwatch Eagle has vigilance as long as it has a +1/+1 counter on it.

Flying
Windwise Courier has indestructible as long as you've revealed a card from your hand this turn.

Flying
Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
As long as Wings of Trust has three or more +1/+1 counters on it, it has lifelink and vigilance.

Flying
Revive {1}{B}{B} ({1}{B}{B}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Armed — Winterborn Savage gets +1/+1 and has vigilance as long as it's equipped.

Harness (You may tap a creature you control as you cast this spell. If you do, reduce this spell's mana cost by that creature's power.)
You gain X life.

Witchseeker Mob's power and toughness are each equal to twice the number of Citizens and/or Peasants you control.
When Witchseeker Mob enters the battlefield, exile target nonland permanent an opponent controls with mana value less than or equal to Witchseeker Mob's power until Witchseeker Mob leaves the battlefield.

Destroy all non-Horror creatures.
Coalesce {8}{W}{W} (You may cast this from your graveyard for its coalesce cost. If you do, put it onto the battlefield as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)