msem-instigator

Menace
Whenever an opponent discards a card, monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous.)

Whenever Twilight Dancer attacks, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Each player loses 1 life and mills a card.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
{1}{B}, Sacrifice a creature: Put a +1/+1 counter on Twisted Cultist.

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
Revive {1}{B} ({1}{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.)

{T}, Pay 1 life: Add one mana of any color that a land an opponent controls could produce.

Colossal 2—{4}{B} (You may cast this for its colossal cost to have it enter with two +1/+1 counters; or pay {4}{B} as a sorcery: Put two +1/+1 counters on it if it has none.)
Lifelink

Vampire Partaker can't block.
Sacrifice a creature: Put a +1/+1 counter on Vampire Partaker. You gain 1 life. Activate only as a sorcery.

Whenever another artifact is put into your graveyard from the battlefield, each opponent loses 1 life and you gain 1 life.

Menace, lifelink
Once during each of your turns, if you would gain life, you may create a tapped Treasure token instead.

Flying
Whenever you cast a spell from exile, each opponent loses 2 life.

Menace
When Vicious Stinger dies, each opponent loses 2 life. You gain life equal to the life lost this way.

Sacrifice Voice of Ambition: Target creature gets +2/+1 until end of turn.

Tithe (When this creature enters, you may tap three other artifacts and/or creatures you control.)
When Wailing Chorus enters, each opponent discards a card. If its tithe was paid, each opponent discards two cards instead.

Deathtouch
When Waking Pollution enters, you may move all counters from target permanent onto Waking Pollution.

{B}, {T}: Destroy target tapped creature.

Deathtouch
Whenever another creature named Winter's Whelp you control enters, you draw a card and you lose 1 life.

{2}{B}, Sacrifice a Clue: Target creature gets -3/-3 until end of turn.

Transcend (Activate as a sorcery to gain the next type and a +1/+1 counter.)
Menace
{2}{B}: Demigod — Surveil 2. Each opponent loses 2 life and you gain 2 life.
{4}{B}: God — Search your library for two cards with different names and reveal them. An opponent chooses one. Put the chosen card into your graveyard and the rest into your hand. Then shuffle.

Double strike

First strike
Whenever a player loses life, creatures you control get +1/+0 until end of turn.

Rapport — Whenever Ainok Lout and at least one other creature you control become tapped, Ainok Lout gets +2/+0 until end of turn.

Haste
Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{1}{R}: Akaima Rager gets +1/+0 until end of turn.

Akroan Truespear has first strike as long as it's attacking.
Heroic — Whenever you cast a spell that targets Akroan Truespear, put a +1/+1 counter on Akroan Truespear.

Frenzy 2 (Whenever this creature attacks and isn't blocked, it gets +2/+0 until end of turn.)
Whenever Aleud Blademaster becomes blocked, it gains double strike until end of turn.

Whenever Almgrove Bladesinger attacks, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Target creature can't block this turn.