msem-instigator

Flying
Spirited (When this creature enters, you may activate one of its activated abilities without paying its costs.)
Harmony — Draw three cards.
{2}{G}{G}: Harmonize. (Trigger up to one harmony of a permanent you control.)

Primal {2}{R}{R} (During your turn, you may cast this spell for {2}{R}{R} instead of playing a land.)
Flying, prowess
At the beginning of your end step, if you didn't cast a spell this turn, sacrifice Thunderstride.

Tyrant of the Depths has hexproof as long as it's untapped.
Whenever you cycle Tyrant of the Depths or it attacks, tap target nonland permanent you don't control and put a stun counter on it.
Basic landcycling {1}{U} ({1}{U}, Discard this card: Search your library for a basic land card, reveal it, and put it into your hand, then shuffle.)

Defender
Venerable Loremaster can attack as though it didn't have defender if it's in a pack. (Two or more creatures you control with equal power are in a pack.)

Whenever Waketide Serpent attacks, you may pay {2}{U}. If you do, tap target creature. It doesn't untap during its controller's next untap step.

Menace (This creature can't be blocked except by two or more creatures.)
When Achet-Aton, Living God enters, if your life total is less than 5, your life total becomes 5.
As long as you have 5 or more life, damage that would reduce your life total to less than 5 reduces it to 5 instead.

Whenever Battle-Scarred Combatant attacks or blocks, put a -1/-1 counter on it.

When Corrupt Warden enters, up to one target creature gets -X/-X until end of turn, where X is the number of card types among cards in your graveyard.

This spell costs {1} less to cast for each card type among cards in your graveyard.
Deathtouch

Deathtouch
Cutthroat Deceiver enters with four -1/-1 counters on it.
{3}{B}, {T}: Move a -1/-1 counter from Cutthroat Deceiver onto another target creature.

All creatures get -3/-2 until end of turn.
Coalesce {6}{B}{B} (You may cast this from your graveyard for {6}{B}{B}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Haste (This creature can attack and {T} as soon as it comes under your control.)
Whenever a creature you control attacks, each opponent loses 1 life.

Indestructible
As long as your devotion to black is less than five, Erebos isn't a creature.
Other creatures you control dying causes abilities of that creature to trigger as though it entered.
{2}{B}: Each opponent loses 1 life. You gain life equal to the life lost this way.

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Cycling {B} ({B}, Discard this card: Draw a card.)

Whenever Halford enters or attacks, an opponent chooses one. When they choose one that has already been chosen, copy that ability.
• That opponent loses 2 life and you gain 2 life.
• That opponent sacrifices a permanent.
• That opponent discards a card. If they can't, draw a card.

Menace
Vanguard — Whenever a creature you control attacks alone, it gets +1/+1 until end of turn for each creature card in your graveyard.

Flying, trample
At the beginning of your upkeep, sacrifice a creature.
Revive {2}{B}{B} ({2}{B}{B}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Flying
Kai'Wej, the Desolate has indestructible as long as you control no other creatures.
{1}{B}{B}, Sacrifice two creatures: Return Kai'Wej from your graveyard to the battlefield tapped.

Flying, lifelink
Other Demons you control have flying and lifelink.
If you would create a creature token, you may instead pay 5 life and create a 5/5 black Demon creature token.

Flying, trample
When Lord of Sacrilege enters, each opponent loses 3 life, discards a card, then sacrifices a nonland permanent. If you control three or more Demons and/or Warlocks, instead each opponent loses 6 life, discards two cards, then sacrifices two nonland permanents.

This spell costs {1} less to cast if you control a Warrior.

Play with the top card of your library revealed.
Whenever you draw a card, destroy each creature with the same mana value as that card.

Menace
Sabotage — Whenever an opponent or permanent an opponent controls becomes the target of a spell you control, each opponent discards a card.

Deathtouch
When Scion of Desolation enters, put target creature card with mana value 3 or less from a graveyard onto the battlefield under your control.
Whenever a Swamp you control enters, you may aetherize Scion of Desolation. (To aetherize, create a token that's a copy of it, then exile that token.)

Enspirit (As you cast this spell, you may exile a nonenchantment creature you control until this leaves the battlefield or fails to resolve. Reduce this spell's cost by the exiled card's mana value.)
Menace