msem-instigator

Harmony — Scry 2.
{T}: Harmonize. Activate only as a sorcery. (Trigger up to one harmony of a permanent you control.)

Flying
Spirited (When this creature enters, you may activate one of its activated abilities without paying its costs.)
{3}{U/B}{U/B}: Look at the top card of target opponent's library, then exile it face down. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any type to cast that spell.

Flying
When Aven Merchant enters, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Flying
When Aven Strategist enters, return up to one target creature to its owner's hand.

This spell costs {2} less to cast if a creature died under your control this turn.
Flying

This spell can't be countered.
Survivor spells you cast can't be countered.
Whenever a nontoken Survivor you control enters, create a tapped 1/1 Survivor creature token that's all colors.

Flash
When Axom enters, remove up to three counters from target permanent.
{2}{U}: Return Axom to its owner's hand.

When Azure Archaeologist enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
{2}, {T}, Sacrifice a Clue: Draw two cards, then discard a card.

When Azutahn Hydromancer enters, you may return target creature with power X or less to its owner's hand, where X is the number of differently named lands you control.

Desecrate (When this creature enters, you may sacrifice an artifact or land.)
When Back-Alley Vandal desecrates a permanent, put a +1/+1 counter on Back-Alley Vandal.

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Whenever Backalley Silencer deals combat damage to a player, destroy target marked creature.

Haste
When Backdrop Artisan dies, audition for red. (Create a 1/1 Construct Actor creature token, a Warrior Role giving 3/2 and trample, or a Wizard Role giving 2/2 and prowess. Roles replace older ones.)

Basic Forests you control have “{G}, {T}: Untap target attacking creature and remove it from combat.”

Whenever you create one or more tokens, put a +1/+1 counter on target creature you control.
{2}{G}{W}: Create a 0/1 green Plant creature token.

Prowess
Whenever Balefire Conjurer attacks, you may pay {1}{R}. If you do, exile the top card of your library. You may play that card until the end of your next turn.

Menace
As long as Balefire Harbinger is attacking, creatures in its pack can't be blocked unless defending player pays {1} and 1 life for each creature they control that's blocking one of those creatures. (Two or more creatures you control with equal power are in a pack.)

Whenever Baljurn, the Runelord or another nontoken artifact or enchantment you control enters, create a 0/0 blue Construct artifact creature token. Put a +1/+1 counter on each artifact and/or enchantment creature you control other than Baljurn.

When Banished Prophet enters, you may remove a counter from a permanent you control. If you do, put a +1/+1 counter on another target creature you control.

When Banishing Initiate enters, you may exile target nonland permanent you don't control until Banishing Initiate leaves the battlefield.
At the beginning of your end step, sacrifice Banishing Initiate if a card exiled with it has mana value 3 or greater.

When Barbarian Hoarders enters, you may attach target Equipment you control to it.

Other Warriors you control have first strike.
Other Barbarians you control get +1/+0.

Battalion — Whenever Barbaric Ambusher and at least two other creatures attack, you may tap target creature.

First strike (This creature deals combat damage before creatures without first strike.)
Other Soldier creatures you control get +1/+1 and have first strike.
{3}{W}: Create a 1/1 white Soldier creature token.

Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever Barrow Banshee deals combat damage to an opponent, that player discards a card at random.