msem-instigator

When Ancestors' Grace enters the battlefield, you may search your library for an enchantment card, reveal it, put it into your hand, then shuffle.
Enchantments you control not named Ancestors' Grace have indestructible.
Enchanted permanents you control have indestructible.

When Ancestral Council enters the battlefield, search your library for an instant or sorcery card with mana value 2 or less, reveal it, put it into your hand, then shuffle.

Flash
When Ancestral Warlord enters the battlefield, it deals 1 damage to each blocking creature.

Trample
When Ancient Pillan enters the battlefield, it fights up to one target creature an opponent controls.

When Ancient Tablet enters the battlefield, scry 2.
{2}, Sacrifice Ancient Tablet: You may shuffle any number of target cards from your graveyard into your library. Draw a card.

Ward {2}
When Ancient of Lotus Lake enters the battlefield, draw a card.

Flying
When Ancient of Reflections enters the battlefield, create a token that's a copy of target creature you control not named Ancient of Reflections, except it's 1/1 and has haste. Sacrifice it at end of turn.

When Ancient of the Glade enters the battlefield, put a +1/+1 counter on each other creature you control.
{2}, Remove a +1/+1 counter from a creature you control: That creature gains indestructible until end of turn.

Flying
When Andazir Assaulter enters the battlefield, recruit. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)

Flash
Flying
When Angel of Redemption enters the battlefield, if another target creature you control would die this turn, exile it instead. Return that card to the battlefield under its owner's control at the beginning of the next end step.

Enchant creature
When Angel's Favor enters the battlefield, draw a card.
Enchanted creature gets +0/+2 and has flying.

Reach
Erratic (When this creature dies, reveal the top four cards of your library. Put a creature card that costs less than this revealed this way onto the battlefield and the rest on the bottom of your library in any order.)
When Angelbane Spider enters the battlefield, destroy target creature with flying.

When Ankulith Shard enters the battlefield, draw a card.
{1}, {T}: Add one mana of any color.

Lifelink
When Anointed Cursebreaker enters the battlefield, you may exile target artifact or enchantment an opponent controls. When Anointed Cursebreaker is no longer on the battlefield, return the exiled card to its owner's hand.

When Anointed General enters the battlefield, if you control a legendary creature, Anointed General deals 4 damage to target creature you don't control.

Flying, vigilance
Augmented — When Antigravity Agent enters the battlefield, if you've spent {W}{U}{R}{B}{G} to cast spells this turn, distribute a flying counter and a vigilance counter among one or two creatures you control.

Flash
When Aokara Redeemer enters the battlefield, exile another target permanent you control. Return that card to the battlefield under your control at the beginning of the next end step.

Flying
When Apogee Cranes 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.”)

When Apprentice Summoner enters the battlefield, search your library for a creature card with mana value 1 or less, put it onto the battlefield, then shuffle.

When Appropriated Gear enters the battlefield, create a Treasure token.
Equipped creature gets +1/+1.
Equip {2}

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
When Arbiter of Shal'Iv enters the battlefield, adjudicate. (Create a white enchantment Aura token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)

Flying
When Arbiter of Silence enters the battlefield, exile all other creatures until Arbiter of Silence leaves the battlefield. (They return to the battlefield under their owners' control.)

Flash
Enchant creature
When Arcane Anesthesia enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Harmony — Attach Arcane Saxophone to target creature.
When Arcane Saxophone enters the battlefield, harmonize. (Trigger up to one harmony of one permanent you control.)
Equipped creature gets +2/+2.
Equip {4}

When Arcanomancer enters the battlefield, return up to one target instant card and up to one target sorcery card from your graveyard to your hand.