msem-instigator

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.

Deception {2}{B} ({2}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Agent of Long Shadows deals combat damage to a player, you may put a Rogue card from your hand or graveyard onto the battlefield.

Menace, haste
Whenever Aiel's Fury attacks, scry 2, then reveal the top card of your library. Aiel's Fury gets +X/+0 until end of turn, where X is that card's mana value.

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

Whenever Ainok Caretaker or another Hound you control attacks, untap that creature and it gets +1/+1 until end of turn.

Trample
Other Hounds you control get +1/+1 and have trample.

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

Frenzy 2 (Whenever this creature attacks and isn't blocked, it gets +2/+0 until end of turn.)
Whenever Airam, Packleader becomes blocked, other creatures you control get +1/+1 until end of turn.

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.

Whenever Akoum Pathfinder attacks, create a 1/1 red Goblin creature token.
Other Goblins you control get +1/+0 and have haste.

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.

Haste
Heroic — Whenever you cast a spell that targets Akroan Siege Captain, put a +1/+1 counter on each creature you control.

Flying
Whenever Albino Drake deals combat damage to an opponent, 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 Alder Courtier dies, you gain 4 life.

At the beginning of your upkeep, you may sacrifice a Goblin. If you do, Alenian Boom Squad deals 2 damage to any target.

Other Goblins you control get +1/+0 and have menace.

Whenever a land you control enters, create a 1/1 red Elemental creature token. Then if you control three or more Elementals, exile Aleryn, Trapseeker, then return him to the battlefield transformed under his owner's control.

Menace
At the beginning of your upkeep, put a prize counter on target permanent you don't control.
Whenever a permanent with a prize counter on it is put into a graveyard from the battlefield, return it to the battlefield under your control.

When Allagras' Vanguard enters, create two 1/1 blue Merfolk creature tokens with “When this creature dies, draw a card, then discard a card”.

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Alley Hunter has lifelink as long as it's blocked by a marked creature.

Alluring Rider must be blocked if able.
Attain {4}{G} ({4}{G}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Lifelink
Whenever you cast a spell, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Almgrove Ensemble deals 1 damage to target player or planeswalker.

Infamy 1 (Whenever this creature deals combat damage to a player, if it has no +1/+1 counters on it, put a +1/+1 counter on it and it becomes infamous.)
When Alpha Scout becomes infamous, create a 2/2 green Wolf creature token.