msem-instigator

When Affluent Host dies, it deals 1 damage to each opponent. Create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
Foreshadow {2}{R} (You may cast this spell for its foreshadow cost. If you do, also trigger its “dies” abilities when it enters.)

When Affluent Knight enters, recruit, then recruit again. (To recruit, create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)

Creatures you control get +1/+1 until end of turn.
Lifecycle {3} ({3}, Discard this card: Create two tapped 1/1 colorless Elemental creature tokens.)

When Ageless Ascetic enters, return up to one target instant or sorcery card from your graveyard to your hand.

Whenever a creature you control dies, put a +1/+1 counter on Agent of Andazir.

Flash
When Agent of Equilibrium enters, destroy target creature or planeswalker an opponent controls that was dealt damage this turn.

Whenever Agent of Vitu-Ghazi deals combat damage to a player, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Poisonous 1 (Whenever this creature deals combat damage to a player, that player gets a poison counter.)
At the beginning of your upkeep, destroy target artifact or enchantment if its controller is poisoned.

Agonizing Syphon deals 3 damage to any target and you gain 3 life.

Enchant land
When Aid from Martoob enters, recruit. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)
When enchanted land is tapped for mana, add one mana of any color.

Move up to one +1/+1 counter from a creature you control to target creature you control. Then that creature fights target creature you don't control.

Rapport — Whenever Ainok Brushwacker and at least one other creature you control become tapped, Ainok Brushwacker gains first strike until end of turn.

Rapport — Whenever Ainok Lout and at least one other creature you control become tapped, Ainok Lout gets +2/+0 until end of turn.

Whenever another creature named Ainok Pack you control enters, you gain 2 life.

Draw a card.
Showcase {3}{U} (Then if you cast this for its showcase cost, create a 1/1 red Bard creature token that can't block and exile this. Whenever it attacks, you may cast a free copy of this.)

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
When Aith Aera Sentinel enters, create a 1/1 green Elf creature token.

Whenever a creature token you control enters, put a +1/+1 counter on target creature you control.

Vigilance
{1}{G}: Ajani's Advocate gets +2/+2 until end of turn. Activate only once each turn.

Haste
Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{1}{R}: Akaima Rager gets +1/+0 until end of turn.

Akimbo Slash deals 1 damage to each of up to two target creatures.
Ferocious — Those creatures can't block this turn if you control a creature with power 4 or greater.

Aurashaper and Aura spells you cast cost {1} less to cast.

Trample
Wanderlust — Whenever Akkrixian Assailants attacks, if you control four or more differently named lands, put a +1/+1 counter on it.

Haste
{R}: Akoum Rockhurler gets +1/+0 until end of turn.
Whenever Akoum Rockhurler attacks, you may sacrifice a land. If you do, put two +1/+1 counters on Akoum Rockhurler.

Vigilance
When Akrasan Sentry enters, untap target creature.

Akroan Truespear has first strike as long as it's attacking.
Heroic — Whenever you cast a spell that targets Akroan Truespear, put a +1/+1 counter on Akroan Truespear.