msem-instigator

{1}{R}: Aravant Throatcutter and up to one other target Pirate or Rogue you control each get +1/+0 until end of turn.

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

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

Whenever Arcane Duelist becomes tapped, target instant or sorcery card with mana value 1 in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost. (You may cast that card from your graveyard for its flashback cost. Then exile it.)

{U}, Exile an instant or sorcery card from your graveyard: Draw a card, then discard a card.
{R}, Exile an instant or sorcery card from your graveyard: Arcane Harvesters deals 1 damage to any target.

Whenever Arcane Metalcrafter or another Wizard you control attacks, create a 1/1 colorless Construct artifact creature token that's tapped and attacking.
Whenever a Construct you control dies, Arcane Metalcrafter deals 1 damage to each opponent.

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

Flying
When Arcanum Owl enters, you may return target instant or sorcery card from your graveyard to your hand.

Lifelink
Arcblade Enforcers gets +1/+1 as long as you control an enchantment.

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 Archivist Heretic enters, you lose 1 life, then investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Whenever Archlegislator attacks, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
{3}{R}{R}, {T}, Sacrifice an Aura: Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn.

When Arcor-Staff Adherent enters, you may remove all -1/-1 counters from target creature.

Whenever Arena Challenger deals damage to a creature, upgrade it. (Give it one of the listed counters it doesn't already have.)
• +1/+1
• First strike
• Prowess

When Aridland Camaar enters, create a 1/1 white Bird creature token with flying.

When Arisen Troops dies, you may destroy target creature that was dealt damage this turn.

As long as Armed Vendor is enchanted or equipped, it gets +1/+0 and has menace.

When Armored Valiant enters, creatures you control get +1/+1 until end of turn.

Whenever two or more creatures an opponent controls attack, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
Enchanted creatures you control get +0/+2.

When Arms Merchant enters, look at the top four cards of your library. You may reveal an artifact card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

When Army Guide dies, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
{2}{G}{W}, Sacrifice Army Guide: Exile target noncreature, nonland permanent. Activate only as a sorcery.

Lifelink
When Army's Suppliers enters, recruit. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)

{T}: Add {G}.
{1}{G}, {T}: Return target land card from your graveyard to the battlefield tapped.