msem-instigator

When Alenian Cruel-Star enters, put a +1/+1 counter on it if you control another Goblin.

Aleud Beastmaster has frenzy X, where X is the number of unblocked attacking creatures you control. (Whenever it attacks and isn't blocked, it gets +X/+0 until end of turn.)

Harmony — Warriors you control get +1/+0 and gain menace until end of turn.
Whenever Aleud Warcaller attacks, harmonize. (Trigger up to one harmony of a permanent you control.)

As long as you have 25 or more life, Alia's Enforcer gets +2/+2 and gains flying.
Whenever an artifact or enchantment you control enters, you gain 1 life.

Flying, first strike, vigilance, trample, lifelink
{4}: Put a +1/+1 counter on Alin and Meva, Warqueens.

Flying
Whenever a creature enters under an opponent's control, you may pay {1}{B}. If you do, fateseal 1. (Look at the top one cards of an opponent's library, then put any number on the bottom and the rest on top in any order.)

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.

Whenever Almgrove Bladesinger attacks, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Target creature can't block this turn.

First strike
Cadence (Whenever you cast a spell, if its mana value is greater than this creature's power, put a +1/+1 counter on this creature.)
Almgrove Champion can only attack or block alone.

Defender
Whenever you cast an instant or sorcery spell, you may untap Almgrove Sentinel.
{T}: Almgrove Sentinel deals 1 damage to any target.

Whenever Almgrove Spellblade attacks, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Exile the top two cards of your library. Until end of turn, you may play cards exiled by Almgrove Spellblade.

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.

Alquyut Mount can't attack or block alone.

Flying
Whenever an artifact you control leaves the battlefield, scry 1.

Althestran Legionnaire gets +1/+1 for each Aura attached to it.

At the beginning of each other player's upkeep, draw a card, then discard a card unless you have Am'atambi, Fable Weaver deal 3 damage to you.
You may reveal creature cards as you draw them. Once each turn, when you reveal a creature card this way, you may pay {3}. If you do, create a token that's a copy of it, except it's 3/3.

Trample
Whenever a Warrior you control dies, it deals 1 damage to any target.

Sacrifice Amateur Auteur: Destroy target enchantment.

Overclock (You may have this creature overclock an artifact you control when either enters. If you do, it stops overclocking any other artifacts.)
Overclocked artifact has “{R}, {T}: This artifact deals 1 damage to any target.”

Sabotage — Whenever an opponent or permanent an opponent controls becomes the target of a spell you control, return target creature card with mana value 3 or less from your graveyard to the battlefield.

Flash
When Ambush Gharial enters, it fights up to one target creature. If that creature would die this turn, exile it instead.

Trample
As long as it's an opponent's turn, Ambushing Alligator is a blue Bird with base power and toughness 1/1 and has flying and hexproof.

Lifelink
At the beginning of each end step, if you gained life this turn, you may pay {W/B}. If you do, create a 1/1 white Spirit creature token with flying.

When Amira, Grand Inventor enters, create a 1/1 colorless Construct Artificer artifact creature token. If you control six or more artifacts, create a 6/6 colorless Golem artifact creature token instead.
Artifact tokens you control have all activated abilities of other artifact tokens you control.

Reach, vigilance
When Amorphous Tyrant enters, another target creature you control deals damage equal to its power to target creature or planeswalker you don't control.
Evoke {G} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)