msem-instigator

Colossal 4—{8} (You may cast this for its colossal cost to have it enter with four +1/+1 counters; or pay {8} as a sorcery: Put four +1/+1 counters on it if it has none.)
Abilities you activate that aren't mana abilities cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Art of war — At the beginning of your end step, if Aokara Duelists dealt damage to an opponent this turn, put a +1/+1 counter on it.

Flash
When Aokara Redeemer enters, exile another target permanent you control. Return that card to the battlefield under your control at the beginning of the next end step.

Flying, lifelink
Improve {1}{W/B} ({1}{W/B}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Once each turn, when you gain life, you may have each opponent lose 2 life.

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

Trample
When Arborback Stomper enters, you gain 5 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.)

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.

Wanderlust — When Ardent Explorers enters, if you control four or more differently named lands, create a 1/1 Scout creature token that's all colors. That token gains haste until end of turn.

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

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 Arisen Helix attacks, scry 2.
If Arisen Helix would die, exile it instead.

Haste
Whenever Arisen Hunter attacks, target player loses 2 life and you gain 2 life.
If Arisen Hunter would die, exile it instead.

Whenever Arisen Rider attacks, creatures your opponents control get -1/-1 until end of turn.
If Arisen Rider or another creature or planeswalker would die, exile it instead.

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

Prevent all combat damage that would be dealt to Armored Axewarden as long as it's embattled. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

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.)

Lands you control have hexproof.
{2}{G}{U}: Rouse 2. (Distribute two +1/+1 counters among permanents you control. If they aren't creatures, tap them and they become 0/0 creatures in addition to their other types.)

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

Winnow (Damage dealt to this creature also causes you to lose that much life.)
{2}{B}: Each creature blocking Arroyo's Servant gains winnow until end of turn.

When Artillery Mage enters, it deals 5 damage to target creature you don't control.
{5}{R}, {T}, Discard a card: Artillery Mage deals 5 damage to target creature you don't control.

Sabotage — Whenever an opponent or permanent an opponent controls becomes the target of a spell you control, Artisan of Brutality gets +2/+0 and gains first strike until end of turn.

Flying
When Ascended Explorer enters, return target creature card with mana value 2 or less from your graveyard to the battlefield.

Ash Freebooter has first strike as long as it's attacking.
When Ash Freebooter enters, you may discard a card. If you do, draw a card.