msem-instigator

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever a creature you control becomes renowned, you gain 2 life.

Gain control of target creature until end of turn.
Coalesce {6}{U}{B} (You may cast this from your graveyard for {6}{U}{B}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
As long as Mortal Whims Falter is on the battlefield, you can't lose control of permanents.

Flying
{1}{W/U}{W/U}: Creatures you control gain flying until end of turn if another creature you control has flying. The same is true for first strike, double strike, deathtouch, haste, indestructible, lifelink, menace, reach, trample, and vigilance.

When Moss Dweller enters, put a +1/+1 counter on another target creature.

Deathtouch
Other creatures you control get -1/-1.
Whenever Mother Night attacks, put target creature card from a graveyard onto the battlefield under your control.

{B}{G}{U}: Mother Roo gets +2/+2 and gains flying until end of turn.

Flying
Whenever another creature you control enters, you gain 1 life.

{4}{G}: Monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous.)
When Mountain Bighorn becomes monstrous, you may have it fight target creature you don't control.

Whenever you tap a land for mana, add one mana of any type that land produced.
Whenever you cast a spell with mana value greater than the number of lands you control, sacrifice a land.

Deception {U}{B} ({U}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Ms. Moxie deals combat damage to a player, you may exile target nonland card with mana value 2 or less from your graveyard. If you do, cast a copy of that card without paying its mana cost.

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.)

Trample, haste
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)
At the beginning of your end step, sacrifice a creature.

When Mukal Swarmhorde enters, put a +1/+1 counter on each other Construct you control.
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

When Mulchborn Behemoth enters, you may sacrifice any number of lands.
Mulchborn Behemoth gets +1/+1 for each land card in your graveyard.
{B}{G}, Sacrifice a land: Destroy target creature or land.

Trample
Whenever Muse of Summer Revelry enters or you cast a spell with power 4 or greater, choose one —
• You gain 3 life.
• Create a 2/2 green Wolf creature token.
• Draw a card.

At the beginning of your upkeep, germinate. Then if creatures you control have total power 10 or greater, transform Mushroom Merchant. (To germinate, put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)

You may have Mutalithic Golem enter as a copy of any land on the battlefield, except it's an artifact in addition to its other types.

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

{T}: Add one mana of any color. If that mana is spent on a legendary creature spell, it enters with an additional +1/+1 counter on it.

When Mystic Mackerel enters, you may have target player mill two cards.
{3}{U}, Sacrifice Mystic Mackerel: Return target enchantment, instant, or sorcery card from your graveyard to your hand.

Reverberate {2}{G} (When you cast this spell, copy it if you paid its reverberate cost. The copy becomes a permanent when it resolves.)
Mystical Echo gets +1/+1 for each other Reflection you control.
Whenever you discard a card, Reflections you control gain trample until end of turn.

{T}: Mystical Elk becomes a copy of target creature card in your graveyard. Activate only as a sorcery. (It loses this ability.)

Haste
Whenever Nadei deals combat damage to a player, that player sacrifices a land. You may put a land card from a graveyard onto the battlefield under your control.

Flying
Whenever Naiala's Guide deals combat damage to a player, draw a card, then discard a card.

When Naive Apprentice enters, each player creates a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
As long as an opponent controls an artifact, Naive Apprentice gets +2/+0.