msem-instigator

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.)

Whenever a creature dealt damage by Mooncursed Howler this turn dies, create a 2/2 red Werewolf creature token with first strike.

Moonshard Crater enters tapped.
{T}: Add {R}.
{2}{R}, {T}: Each player sacrifices a nonbasic land.

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

Motley Crew has no name while it's being cast. (It will always make first contact.)
{2}{R}: Creatures you control named Motley Crew get +1/+0 until end of turn.

(Transform this if it's not attached to a creature. Pay {3}{R}{R} as a sorcery to unattach it.)
Enchant creature you control
Mount of the Order's rider gets +5/+4.
{2}{R}: Target creature can't block Mount of the Order's rider this turn.

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

When Mouthpiece of Yhzag enters, you may have target opponent create a tapped 1/1 colorless Human creature token.
Whenever Mouthpiece of Yhzag attacks, gain control of target Human creature you don't control with mana value 3 or less until end of turn. Tap it. It's attacking.

Until end of turn, target creature gets +2/+2 and gains “Whenever this creature attacks, you may post a bounty on target creature.” (Put a bounty counter on that creature. It has “When it dies, each opponent draws a card” as long as it has a bounty counter on it.)

Haste
Whenever Mukal Charger attacks during your first combat phase each turn, untap all Constructs you control. After this phase, there's an additional main phase followed by an additional combat phase.
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

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

As an additional cost to cast this spell, pay {3} or discard a card.
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.)

Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)
Whenever Mukal Warleader attacks, the next Construct spell you cast this turn costs {1} less to cast.

As an additional cost to cast this spell, pay {2} or put a -1/-1 counter on a creature you control.
Munitions Explosion deals 3 damage to any target.

Enchant creature
Whenever enchanted creature attacks, it gets +3/+3 and gains trample until end of turn.

Untap all creatures that attacked this turn. After this main phase, there is an additional combat phase followed by an additional main phase. For each planeswalker you control, you may activate its loyalty abilities an additional time this turn.

First strike
When Mutilated Warrior enters, you may have it deal damage to each player equal to the number of Warriors you control.

Menace
Other attacking Hounds you control get +2/+0.

(As you complete a condition, decode it. After all are decoded, you solve the mystery and transform this.)
When Mystery of the Crashed Craft enters, create two 1/1 red Alien creature tokens with “This creature can't block.”
{MG}—You cast an instant spell.
{MG}—You cast a sorcery spell.

{R}, Sacrifice Nacatl Skirmisher: Destroy target artifact.
Stampede — Whenever Nacatl Skirmisher and a creature with greater power attack, creatures you control get +1/+0 until end of turn.