msem-instigator

Whenever one or more creatures you control deal combat damage to a player, that player discards a card. Then that player may discard another card. If they don't, create two 2/1 black Nightmare creature tokens with “This creature can't block.”
Fleeting {1}{B}{B} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

Unvirtuous Maestro can't be blocked except by three or more creatures.

Venerated Beast can't be blocked by more than one creature.

Flying, haste
Volcano Tyrant enters with a first strike counter on it.
{2}{R}, Remove a first strike counter from Volcano Tyrant: Double its power and it gains trample until end of turn.

At the beginning of combat on your turn, create a token that's a copy of another target nonlegendary creature that crewed Voyager's Ark this turn. That token gains haste.
Crew 3 (Tap any number of creatures you control with total power 3 or greater: This Vehicle becomes an artifact creature until end of turn.)

Vanishing 1 (This creature enters with a time counter on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
When Waning Behemoth enters, you may pay {X}. If you do, put X time counters on it.

Protection from instants and from sorceries
When Warbringer Titan enters or attacks, create two 1/1 white Soldier creature tokens with melee. (Whenever that creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)

Target player mills two cards.
Draw a card.
Coalesce {6}{U} (You may cast this from your graveyard for {6}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Put two +1/+1 counters on up to one target creature.
Coalesce {6}{G}{G} (You may cast this from your graveyard for {6}{G}{G}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

You may exert Wiedfree Behemoth as it attacks. When you do, it gets +3/+3 and gains trample until end of turn. (An exerted creature won't untap during your next untap step.)

Wildfire Elemental has frenzy 4 as long as you control no other creatures. (Whenever this creature attacks and isn't blocked, it gets +4/+0 until end of turn.)
Wildfire Elemental has frenzy 4 as long as you have no cards in hand.

Vigilance, reach
When Winter Widow enters, you may destroy target creature with flying.

Each player shuffles their hand and each non-Revelation card from their graveyard into their library, then draws seven cards. You may put any number of land cards from your hand onto the battlefield.
Coalesce {6}{G}{U}{U} (You may cast this from your graveyard for {6}{G}{U}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Trample, vigilance
Spells your opponents cast that target Xiejuan and Hao Lu cost {X} more to cast, where X is the number of other creatures you control.
Whenever another creature you control dies, draw a card.

Alpha (You may have this creature enter with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)
When Xiejuan, the Regal Beast becomes alpha, draw a card for each other creature you control.

When Ziggurat Behemoth enters, target creature gets +3/+3 until end of turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

Each player mills four cards.
Coalesce {5}{U}{U} (You may cast this from your graveyard for {5}{U}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
When A Vision Too Vast enters, you may cast target noncreature, nonland card with mana value 4 or less from a graveyard without paying its mana cost.

Legendary spells you cast have nonlegendary cascade. (When you cast that spell, exile cards from the top of your library until you exile a nonlegendary nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Wither (This deals damage to creatures in the form of -1/-1 counters.)
Abyssal Accuser must be blocked if able.

Haste
Disgraced 1 (This enters with a -1/-1 counter. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)

Flying
Whenever Acabo, the Fabled Falcon attacks, you choose how up to one target creature an opponent controls blocks this turn.

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.

Civilized — Adorned Naga gets +2/+0 and has menace as long as you control an artifact, a creature, and an enchantment.

When Aerie Bell-Warden enters, if it's in a pack, you gain 5 life. (Two or more creatures you control with equal power are in a pack.)