msem-instigator

When Fang Den Headhunter enters, look at the top card of your library. If it's a creature card, you may reveal it and draw a card.

Counter target spell, activated ability, or triggered ability unless its controller pays {X}. (Mana abilities can't be targeted.)

{R}: Charbelcher gets +1/+0 until end of turn.

When Mystic Seer enters, each player may scry 1.
{2}{U}: Draw a card, then discard a card.

Destroy target attacking or blocking creature.

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.

Enchant creature
Enchanted creature has deathtouch and “{1}{B}: Regenerate this creature.”

Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever a creature with wither deals combat damage to an opponent, Scorchmark Seer deals 2 damage to that player.

Indestructible
As long as your devotion to white and black is less than seven, Athreos isn't a creature.
Other creatures you control have lifelink.
Each player and cards in graveyards can't be the targets of spells or abilities your opponents control.

{T}, Sacrifice a creature: Conjure a card named Data-Point into your hand. Activate only as a sorcery. (It's a sorcery that costs {2} with “Draw a card.”)

{T}, Sacrifice Daunting Skyline: Search your library for a Plains or Swamp card and put it onto the battlefield tapped, then shuffle.

Return target card from your graveyard to your hand. Distribute X +1/+1 counters among any number of creatures you control, where X is that card's mana value. Exile Entropic Harvest.

This spell costs {2} less to cast if its target has the same name as a card in a graveyard.
Scoff deals 3 damage to any target.

Gain control of target nonland permanent if you control a permanent with a greater mana value. Otherwise, destroy that permanent.

Trample
Art of war — At the beginning of your end step, if Imperial Legion dealt damage to an opponent this turn, put two +1/+1 counters on it.

Menace (This creature can't be blocked except by two or more creatures.)
Sacrifice another creature: Stingbrood Warlord gains deathtouch until end of turn.

Enchant creature
Enchanted creature has “At the beginning of each player's end step, that player chooses another creature they control. That creature fights enchanted creature.”

If a permanent with spirited entering the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Whenever you draw a card, put a +1/+1 counter on Sage of Wilds.
Augmented — {T}: Scry 1, then draw a card. Activate only if you've spent {W}{U}{B}{R}{G} to cast spells this turn.

{3}{U}: Draw a card.
{2}{R}: Necropolis Battlemage deals 1 damage to target player. Scry 1.

Ferocious — At the beginning of each combat, if you control a creature with power 4 or greater, Impressible Cub gets +1/+1 until end of turn.

Flying, haste
Whenever Grieving Revenant attacks, it deals 1 damage to each other creature you control.

{2}, Sacrifice another creature: Create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)

Create a 2/2 white Angel creature token with flying.
Coalesce {6}{W}{W} (You may cast this from your graveyard for {6}{W}{W}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
Flying

{1}, {T}, Sacrifice a creature: Search your library for a creature card with mana value 1, put it onto the battlefield, then shuffle. Activate only as a sorcery.