msem-instigator

First strike
Whenever you discard a card, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

When Flare Blitz enters, it deals 3 damage to any target and you gain 3 life.
{1}{R}{W}: Return Flare Blitz to its owner's hand.

Vigilance
Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{2}{W}{W}: Creatures you control get +1/+1 until end of turn.

Whenever you cast a noncreature spell, judge target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

Until end of turn, noncreature lands you control become 3/3 Elemental creatures with haste and trample.
Orchestrate {1}{G} (You may exile this card from your hand anytime you could cast a sorcery for its orchestrate cost. When you next resolve a spell, you may cast this from exile without paying its mana cost.)

Whenever you sacrifice one or more permanents, put a +1/+1 counter on Marsh Dweller.

Flying
You pay {0} to cast your first spell each turn rather than its mana cost. If you cast a spell with {X} in its mana cost this way, X is 8.

Whenever another nontoken creature you control enters, that creature gains haste until end of turn. Then Tremor Seer deals 1 damage to any target.

At the beginning of combat on your turn, you may have Regurgitator Ooze consume. If you do, it gets +2/+2 until end of turn. (To consume, sacrifice another creature or exile a creature card from your graveyard.)
When Regurgitator Ooze dies, return a card exiled with it to its owner's hand.

Whenever one or more cards are put into an opponent's graveyard from their hand or library, Cackling Tormentor deals 2 damage to any target.

Flying
Other Vampire creatures you control get +1/+0 and have menace.

Whenever a creature dealt damage by Mooncursed Howler this turn dies, create a 2/2 red Werewolf creature token with first strike.

Poisonous 3 (Whenever this creature deals combat damage to a player, that player gets three poison counters.)
When Sankataar Assailant enters, choose a counter on target permanent or player. Give that permanent or player another counter of that kind.

When Street Performer enters, create a 2/1 blue Illusion creature token with “When this creature becomes the target of a spell or ability, sacrifice it.”

Reach
Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Other Elementals you control get +1/+1 as long as Miroran Skycatcher has a +1/+1 counter on it.

Bloodprice {B}{B}{B}{B} (You may cast this card by sacrificing a creature and paying its bloodprice.)
Lifelink, haste
Sacrifice another Demon: Jejun, Dark Hunter gains flying and indestructible until end of turn.

Harvest (You may tap any number of creatures you control as you cast this spell. If you do, reduce this spell's mana cost by their total power.)
Draw three cards.

Flying, first strike
If one or more tokens would be created under your control, those tokens plus a 1/1 black and red Vampire creature token with menace are created instead.
{3}{B}{B}: Each opponent loses X life and you gain X life, where X is the number of Vampires you control.

Advance {4}{B}{B} (Cast this for {4}{B}{B} to advance it as it enters. {4}{B}{B}: Advance this as a sorcery.)
Flying
Whenever Valinov Siphoner advances, target player loses 2 life and you gain 2 life.

First strike
Engage (This creature must be blocked each combat if able.)

Destroy target artifact, enchantment, or creature with slipstream.
You gain 4 life.

You may spend mana as if it was mana of any color to cast cards exiled with Marilye.
[+1]: Exile the top card of each opponent's library. Until end of turn, you may cast spells from among those exiled cards.
[–3]: Exile target creature. You may cast that card. If you don't, return it to its owner's hand.
[–7]: Gain control of up to five target nonland permanents.

Trample
Whenever Openmaw Demon or another Azra or Demon you control enters, you may exile target card from a graveyard.

Chiseled Cliffside enters tapped unless you have two or more opponents.
{T}: Add {R} or {W}.