msem-instigator

Armies you control attack each combat if able.
At the beginning of combat on your turn, recruit. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)

Flash (You may cast this spell any time you could cast an instant.)
When Majestic Hippocamp enters, target creature gets -2/-0 until end of turn.

First strike
When Majestic Monitor enters, if you control a legendary creature, creatures you control get +1/+0 and gain haste until end of turn.

Majestic Nauticorn has first strike as long as it's attacking.
Cycling {W} ({W}, Discard this card: Draw a card.)

Pressure {G} (You may cast this spell for its pressure cost if there are seven or more cards in your graveyard.)
Deathtouch

When Manglehorn Hunter enters, draw a card and you lose 1 life.

Maniac Macaque attacks each combat if able.
Whenever Maniac Macaque becomes blocked by a creature, Maniac Macaque deals 1 damage to that creature.

Menace
Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)

Menace, haste
Whenever Manic River-Fishers attacks, you may search defending player's library for an instant or sorcery card that shares a name with a card in their graveyard and cast it without paying its mana cost. That player shuffles.

First strike
Manifold Manipulator has lifelink as long as you control a white permanent. The same is true for flying and blue, menace and black, and trample and green.

When Marauding Goliath becomes blocked by a creature with power 1 or less, sacrifice it at end of combat.

Improve {1}{W} ({1}{W}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Prevent all combat damage that would be dealt to attacking embattled creatures you control. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Whenever Maritime Thug becomes tapped, it deals 1 damage to each opponent.

Menace (This creature can't be blocked except by two or more creatures.)

Menace (This creature can't be blocked except by two or more creatures.)
Whenever a nontoken creature you control dies, exile the top card of your library. You may play that card until the beginning of your next end step.

{1}{G}: Marrow Gorger must be blocked this turn if able.

Whenever Marshback Knights becomes the target of a spell or ability an opponent controls, counter it unless they pay {3}.
{1}{U}: Marshback Knights gains flying until end of turn.

Whenever another creature you control enters, you may pay {2}. If you do, judge that creature. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

First strike

Sacrifice Masahita's Servant: Exile the top card of your library. Until end of turn, you may play that card.

At the beginning of your upkeep, exile the top card of your library. Masahita, Bloodtongue deals damage to you equal to that card's mana value. Until end of turn, you may play that card.

Art of war — At the beginning of your end step, if Masamori Ranger dealt damage to an opponent this turn, search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

First strike
When Masha Ritualist enters or whenever you cast a spell, if {B}{G} was spent to cast it, return target creature card with mana value 3 or less from a graveyard to the battlefield under your control. Put a +1/+1 counter on Masha Ritualist.

When Masha's Lightbound becomes tapped for the first time each turn, untap Masha's Lightbound and each other creature you control.
{W}, {T}: Exile target card from a graveyard.

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Masked Lancer has first strike as long as it's attacking.
Whenever Masked Lancer mentors a creature, that creature gains first strike until end of turn.