msem-instigator

Flash
Flying

Apostle of the Elders has lifelink as long as it has a +1/+1 counter on it.

Whenever Apostle of the Spirit Moon becomes blocked by a creature, Apostle of the Spirit Moon deals 1 damage to that creature and that creature's controller.

Escalate {2} (Pay this cost for each mode chosen beyond the first.)
Choose one or more —
• Search your library for a card, put it into your hand, then shuffle.
• Return target card from your graveyard to your hand.
• Add {B}{B}{G}{G}.

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

As Approach the Dark Tomb enters, choose life or death.
• Life — Whenever you cast a creature spell, you may pay 1 life. If you do, draw a card.
• Death — Whenever a creature you control dies, you may pay 1 life. If you do, draw a card.

Counter target spell. Draw a card, then discard a card.

At the beginning of your upkeep, you may pay {1}{G/U}. If you do, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)
At the beginning of your end step, you may pay {1}{G/U}. If you do, populate. (Create a token that's a copy of a creature token you control.)

Whenever Aravant Smuggler deals combat damage to an opponent, if it's embattled, draw a card. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Vigilance
If another creature would die, exile it instead.
At the beginning of your upkeep, return each creature card exiled with Arbiter of Endless Summer to the battlefield under its owner's control.

{2}{B}, Sacrifice a creature: Draw a card. You gain 1 life.

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

Enchant creature
Enchanted creature gets +1/+1 and has flying and prowess.

Counter target spell. If that spell is countered this way, until the end of your next turn the next spell you cast that shares a type with it costs {X} less to cast, where X is the countered spell's mana value.

Counter target spell.
Look at the top three cards of your library. Put one on top and the rest on the bottom in any order.

When Archaeomancer enters, return target instant or sorcery card from your graveyard to your hand.

When Architect of the Derezzed enters, create two 1/1 colorless Servo artifact creature tokens.
Sacrifice an artifact: Target creature can't be blocked this turn.

When Archive Guardian enters, return target card from your graveyard to your hand.
Recite {1}{B}{G} (You may cast this creature from your graveyard for its recite cost. If you do, exile it when it enters or if it would leave the battlefield.)

Reach
When Archived Intelligence enters, surveil 2. Then if you control a token, draw a card.

When Arisen Haploc enters, return target creature card from a graveyard to its owner's hand.
Revive {5}{B}{B} ({5}{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.)

Whenever an artifact or enchantment you control enters, Armament Scavenger gets +1/+0 and gains trample until end of turn.

Prowess
When Arms Tinkerer enters, choose one —
• Destroy target artifact.
• Create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Haste
Whenever Arpechian Tiger attacks, you may sacrifice a land. If you do, Arpechian Tiger deals 3 damage to target creature or planeswalker.

Once during each of your turns, when a card is put into a graveyard from anywhere, you may cast it. You may spend mana of any color to cast that spell.
When Arroyo, Infinitely Branching is put into your graveyard from anywhere, you may cast it.

Gain control of target creature with the least power among creatures on the battlefield, then invigorate 2. (Choose a creature with the least power among creatures you control and put two +1/+1 counters on it.)