msem-instigator

Motivate 1 (When this creature enters, you may motivate target creature with less power than this by putting a +1/+1 counter on it.)
When Merthilios' Escort motivates a creature, that creature gains first strike until end of turn.

Embellish {4}{W} (If you cast this spell for {4}{W}, create a 1/1 blue Thopter artifact creature token with flying when it enters.)
When Meticulous Mechanist enters, scry 1.

When Mettalia's Forward enters, you may salvage a card. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

Mettalia is all colors.
Mettalia has protection from each color among cards she's salvaged in exile.
When Mettalia enters, for each color, you may salvage a nonlegendary card of that color. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

Mianju enters with your choice of a menace or +1/+1 counter on them.
Whenever two or more creatures in Mianju's pack attack, mill three cards, then return a creature card from your graveyard to your hand. (Two or more creatures you control with equal power are in a pack.)

When Miasma Spewer enters, you may sacrifice a permanent. When you do, Miasma Spewer deals 1 damage to each opponent and each creature and planeswalker they control.

Flash
Wanderlust — When Microzoologist enters, search your library for a creature card with mana value 1. If you control four or more differently named lands, you may search for a creature card with mana value 3 or less instead. Reveal that card, put it into your hand, then shuffle.

Flying
When Midnight Visitor enters, you may return target creature to its owner's hand.

Haste
{R}, {T}: Miede-District Enforcer deals 2 damage to target creature that entered this turn or player that cast a creature spell this turn.
Paranoia {1}{R} (You may cast this spell for its paranoia cost when a permanent you control leaves the battlefield.)

Ferocious — Whenever a creature with power 4 or greater you control enters, Mieng, Who Dances With Dragons becomes a 4/4 Dragon creature with flying until end of turn.

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
Mighty Xioshu can't be blocked by creatures with power 2 or less as long as you're in a renaissance.

Whenever you gain life, Militant Youth gets +1/+1 until end of turn.

When Militia Commander enters, create a 1/1 white Peasant creature token.
Other Citizens and Peasants you control get +1/+1.

When Militia Surgeon enters, you gain 2 life.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Flying
Mind's Contagion has haste as long as there are two or more creature cards in your graveyard.
Whenever Mind's Contagion deals combat damage to a player, until your next turn, it gains “Noncreature spells opponents cast cost an additional 2 life to cast.”

Whenever you cast an instant or sorcery spell, target player mills a card.

Lifelink
Mind-Pryer gets +1/+1 as long as an opponent has one or fewer cards in hand.
Whenever an opponent discards a card, Mind-Pryer cackles. (Put a menace counter on it. If it already has menace, it deals 1 damage to each opponent instead.)

Whenever Ming Fleet Privateer attacks, put a menace counter on target creature in its pack. (Two or more creatures you control with equal power are in a pack.)

At the beginning of combat on your turn, create a 1/1 red Cleric creature token with haste.
At the beginning of your end step, sacrifice each Cleric token you control unless you've cast an instant or sorcery spell this turn.

Colossal 3—{6}{R} (You may cast this for its colossal cost to have it enter with three +1/+1 counters; or pay {6}{R} as a sorcery: Put three +1/+1 counters on it if it has none.)

Menace
When Minotaur Skullsmasher enters, choose a nonland card type. Then target opponent reveals their hand. You choose a card of the chosen type from it. That player discards that card.

Deathtouch
When Mire Triton enters, mill two cards and you gain 2 life.

Prowess

Whenever you sacrifice a permanent, Mischievous Maolu gets +1/+1 until end of turn and you gain 1 life.

Flash
Flying
When Mischievous Sprite enters,you may tap or untap target permanent.