msem-instigator

Flash
When Mokuteki Ambusher enters, until end of turn, other creatures you control gain “{T}: This creature deals 1 damage to any target.”

When Monastery Scribe enters, return target instant or sorcery card from your graveyard to your hand.

Deathtouch
Mirage {1}{B} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

When Monk of Mid-Autumn enters, choose one —
• Put a double strike counter on Monk of Mid-Autumn.
• Destroy target artifact or enchantment.
• Monk of Mid-Autumn deals 2 damage to target tapped creature and you gain 2 life.

Whenever Moon-Scarred Tuzi attacks, target creature in its pack gains first strike until end of turn. (Two or more creatures you control with equal power are in a pack.)

Moonlight Curator has flying as long as it's embattled. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Flying
Whenever another creature with flying you control enters, put a +1/+1 counter on Moonlight Strix.

Once each turn, when another nontoken creature is returned to your hand from the battlefield, you may create a token that's a copy of that creature.

Whenever Morbid Mimic enters or attacks, exile up to one target creature card from a graveyard.
Morbid Mimic has all activated abilities of cards exiled with it.

When Morose Bohemian enters, scry 1, then draw a card.

Prowess, trample
When this creature transforms into Mortal Frame, add {R}{R}{R}.

Players can't gain life.
At the beginning of each player's upkeep, if that player has 10 or less life, they lose 1 life.

Deathtouch

When Moth-Heart Husk dies, create a 1/1 black Spirit creature token with flying.
Revive {3}{B} ({3}{B}, Exile this card from your graveyard: Create a token that's a copy of this card, except it has no mana cost. Activate this ability only any time you could cast a sorcery.)

Whenever you sacrifice a permanent, you may put a -1/-1 counter on target creature.

Flying
When Mother of Owls dies, you may return target creature an opponent controls to its owner's hand.

Kicker {2}{R} (You may pay an additional {2}{R} as you cast this spell.)
Haste (This creature can attack and {T} as soon as it comes under your control.)
If Mountain Victor was kicked, it enters with two +1/+1 counters on it.

First strike, haste
When Mounted Marksman enters, it deals 2 damage to target creature you don't control.

First strike
Whenever a creature dealt damage by Mournful Newborn this turn dies, transform Mournful Newborn.

Double strike

Sacrifice another colorless creature: Put a +1/+1 counter on target creature.

Haste
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

Trample
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

When Mukal Reaper enters, you draw a card and you lose 2 life.
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

Whenever Mukal Sire or another Construct you control enters, Mukal Sire deals 1 damage to each opponent.
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)