msem-instigator

When Slayer's Grimoire enters, exile target non-Human creature an opponent controls until Slayer's Grimoire leaves the battlefield.
{2}{W}, {T}: You gain 2 life.

Identity — As long as you control at least two other creatures that share a creature type with Slicing Steer, Slicing Steer and creatures you control that share a creature type with it get +1/+0 and have menace.

Creatures your opponents control get -4/-0 until end of turn.
Quickdraw {1}{U}{U} (When a creature you control blocks or becomes blocked, you may cast this spell for {1}{U}{U}.)

Ward {2}
Slippery Bunyip can't be blocked except by creatures with Adventures.

Menagerie — {1}{G}: Slipsand Hornshell gains indestructible until end of turn. Tap it. Activate only if there are five or more creature types among creatures you control.

Vanguard — Whenever a creature you control attacks alone, you may exile target instant or sorcery card from your graveyard. If you do, you may cast that spell from exile until your next turn. If that spell would be put into a graveyard, exile it instead.

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Slums Thug gets +1/+1 and has menace as long as you've gained life this turn.

Destroy target creature with power 4 or greater.

Exile target permanent. Smite the Unruly deals damage equal to that permanent's mana value to its controller and you gain that much life.

Smiting Helix deals 3 damage to any target and you gain 3 life.
Flashback {R}{W} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

{2}, Return a creature you control to its owner's hand: Smooth Musician gets +1/+1 and gains lifelink until end of turn.

Target nonland permanent's owner puts it on the top or bottom of their library.

When Snagged Truck enters, investigate three times. (Create three colorless Clue artifact tokens with “{2}, Sacrifice this: Draw a card.”)
Snagged Truck can't attack or block as long as you control a Clue.
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

Enchant creature
Enchanted creature has poisonous 3. (Whenever that creature deals combat damage to a player, that player gets three poison counters.)

Sneaking Capuchin can't be blocked except by creatures with defender.
{U}: Counter target spell or ability that targets Sneaking Capuchin.

Tap up to two target permanents. They don't untap during their controller's next untap step. You may put Snooze into its owner's library third from the top.

You may have Snowfield Doppelganger enter as a copy of any creature on the battlefield, except it has “While a player is choosing targets as part of casting a spell, that player must choose at least one other creature that shares a name with this creature if able.”

As an additional cost to cast this spell, discard a card.
Draw two cards and crystallize twice. (Put a +1/+1 counter on a creature you control or create a Treasure. Then do it again.)

Flying
When Soaring Skymage enters, mill four cards. You may return a creature card with flying from among the milled cards to your hand.

Target player mills six cards. Return each creature that shares a name with a card milled this way to its owner's hand.
Prophecy {1}{U} (Once each turn, you may exile a card with prophecy as you reveal it. When you do, you may cast it for its prophecy cost as long as it's exiled.)

Solar Hatching deals 4 damage to each creature.
Coalesce {6}{R}{R} (You may cast this from your graveyard for {6}{R}{R}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
When Solar Hatching enters, each player chooses up to two lands they control and sacrifices the rest.

When Solar Pact enters, return up to two cards with different mana values from your graveyard to your hand.
Each player can't draw more than one card each turn.

First strike

Target opponent separates all creatures into two piles. You choose one of those piles. For each creature in the chosen pile, its controller sacrifices it.

Whenever Soli Arbalist or a nontoken Angel or Nephilim you control enters, amass Soldiers 2. If it was an Angel, amass Soldiers 4 instead. (To amass Soldiers {2}, put two +1/+1 counters on an Army you control. It's also a Soldier. If you don't control one, create a 0/0 black Soldier Army creature token first.)