msem-instigator

When Artistic Vision enters the battlefield, create two 1/1 colorless Construct artifact creature tokens.
Whenever you cast an instant or sorcery spell, you may tap two untapped artifacts you control. If you do, copy that spell. You may choose new targets for the copies.

Flying
When Ascended Explorer enters the battlefield, return target creature card with mana value 2 or less from your graveyard to the battlefield.

Flash
When Ascetic of Imbalance enters the battlefield, draw two cards, then discard two cards. If you discarded two cards that don't share a type, Ascetic of Imbalance deals 2 damage to any target.

Flying
When Ascetic of the Folded Fan enters the battlefield, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
Each creature you control with a +1/+1 counter on it has vigilance.

Ash Freebooter has first strike as long as it's attacking.
When Ash Freebooter enters the battlefield, you may discard a card. If you do, draw a card.

When Asham's Path enters the battlefield, you gain 8 life.
{1}{W}{W}: Transform Asham's Path. Activate only if your fealty to Plains is five or greater.

Flying, trample
When Ashen Persecutor enters the battlefield, target opponent reveals their hand. You choose a nonland card from it. That player discards that card and you gain life equal to its mana value.

Trample
When Ashka Ritualist enters the battlefield or whenever you cast a spell, if {R}{W} was spent to cast it, create two 1/1 red and green Warrior creature tokens. Put a +1/+1 counter on Ashka Ritualist.

Flash
When Assassin of Fahrib enters the battlefield, choose one —
• Destroy target creature that was dealt damage this turn.
• Scry 2.

When Astrid, Disgruntled Princess enters the battlefield, destroy target creature with mana value less than or equal to the number of Warriors you control.

When Astute Prophet enters the battlefield, draw a card. If you control a legendary creature, draw two cards instead.

When Astute Sceneweaver enters the battlefield, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

Flying
When Atieh's Elite enters the battlefield, judge another target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)
Whenever you honor a creature, until end of turn, that creature has base power and toughness 4/4, gains flying, and becomes an Angel in addition to its other types.

When Atlas of Worlds enters the battlefield, search your library for any number of land cards with different names and exile them, then shuffle.
You may play lands exiled with Atlas of Worlds.

When Atrocity of Flesh enters the battlefield, destroy target nonland permanent.
When Atrocity of Flesh dies, you may exile it. If you do, return target card from your graveyard to your hand.

First strike (This creature deals combat damage before creatures without first strike.)
When Attended Knight enters the battlefield, create a 1/1 white Soldier creature token.

When Attuned Ancient enters the battlefield, if you control a legendary creature, you may have Attuned Ancient deal damage equal to its power to target creature an opponent controls.

Haste
Augmented — When Attuned Lifeform enters the battlefield, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on each creature you control. They gain vigilance until end of turn.

Tribute 3 (As this creature enters the battlefield, an opponent of your choice may put three +1/+1 counters on it.)
When Atuum Serpent enters the battlefield, if tribute was paid, it gains defender. (This effect lasts indefinitely.)

Flash
When Augmented Spawn enters the battlefield, create a 1/1 blue Merfolk creature token for each Island you control.
{U}, Sacrifice a Merfolk: Augmented Spawn gains hexproof until end of turn.

Flying
When Augur of Bleak Horizons enters the battlefield, you gain 3 life and you mill three cards.

Augury Hydra enters the battlefield with X +1/+1 counters on it.
When Augury Hydra enters the battlefield, scry Y, where Y is its power, then draw Y cards.

Enchant creature
When Aura of Leadership enters the battlefield, create four 1/1 white Human Soldier creature tokens.
Enchanted creature gets +2/+2.

When Auramancer enters the battlefield, you may return target enchantment card from your graveyard to your hand.

When Aureate Golem enters the battlefield, create a Treasure token. Each other player creates a tapped Treasure token. (They're artifacts with “{T}, Sacrifice this artifact: Add one mana of any color.”)