msem-instigator

You may exert Accursed Bear as it attacks. When you do, it gets +1/+0 and gains trample until end of turn. (An exerted creature won't untap during your next untap step.)

Exile target creature. At the beginning of the next end step, return that card to the battlefield under its owner's control with your choice of X counters on it from among +1/+1, flying, first strike, lifelink, or vigilance.

Improve {1} ({1}: 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 one or more counters are put on a permanent you control, create a 1/1 colorless Human creature token.
Whenever you attack with three or more creatures, destroy up to one target artifact or enchantment.

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.

[+1]: Create a 1/1 green Saproling creature token. You gain 2 life.
[0]: Creature spells you cast this turn can't be countered. As they enter, they gain hexproof until your next turn.
[–2]: Create a green enchantment token named Survival with “You and other permanents you control have ward {1}.”

Whenever a nontoken creature you control enters, create a 1/1 colorless Human creature token.

Enchant land
Whenever enchanted land is tapped for mana, its controller adds an additional {G}.
{1}{G}, Sacrifice Allure of the Woods: Draw a card.

Amid Flames deals 5 damage to target creature or planeswalker.
You may sacrifice a land. If you do, draw a card.

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.)

Enchant creature
When Anxious Worries enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Trample
When Arborback Stomper enters, you gain 5 life.

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.

Whenever one or more creatures you control deals combat damage to a player, you may sacrifice one of them. When you do, destroy target creature defending player controls, then you and the destroyed creature's controller draw a card.

{B}: Remove a counter from target permanent.
{3}{B}: Move a counter from target permanent onto Ashfeaster Ghouls. Ashfeaster Ghouls can't be blocked this turn.

When Asking Imp enters, an opponent may pay 2 life. If they do, return Asking Imp to its owner's hand.

When Assurance of Finality enters, you may discard a card. If you do, draw two cards.
{1}, Sacrifice Assurance of Finality: Creatures you control gain haste until end of turn.

Once each turn, when Atal, the Shroudmaker enters or you attack with one or more Horrors, you may create two tapped 1/1 colorless Human creature tokens. If Atal isn't a token, creatures you control gain flying until end of turn.
{2}{W}{W}, Discard Atal: Create a token that's a copy of Atal, the Shroudmaker, except it's 4/4 and isn't legendary. Activate only as a sorcery.

Once each turn, when you cast a noncreature spell, create a 1/1 colorless Human creature token. Put a prowess counter on it.

You may exert Awoken Elemental as it attacks. When you do, Awoken Elemental fights another target creature. (An exerted creature won't untap during your next untap step.)

Flying, deathtouch

Flying
When Battlefront Scavenger enters, return target creature card with mana value 3 or less from your graveyard to your hand.

If you control ten or more nonland permanents, you get an emblem with “At the beginning of your end step, return target permanent card from your graveyard to the battlefield.”
Destroy all nonland permanents.

When Belief in the World enters, you may tap two untapped creatures you control. If you do or you control two or more Spirits, search your library for a Spirit card, reveal it, put it into your hand, then shuffle.
Creatures you control get +1/+1.

[+1]: Creatures you control get +1/+0 and gain haste until end of turn.
[0]: Bennett Brooks deals 2 damage to each opponent. If you have an insight counter, create two Treasure tokens.
[0]: You get an insight counter.
[–2]: Sacrifice an artifact. If you do, return target artifact card from your graveyard to the battlefield.

When Benthic Tidebreaker enters, reveal the top card of each player's library and exile one of those cards. You may play that card for as long as it remains exiled, and you may spend blue mana as though it were mana of any color to cast it.
Evoke {1}{U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)