msem-instigator

{T}: Add {C}.
{1}, {T}, Sacrifice Morphic Verge: Choose two different basic land types. Create a colorless land token that's the chosen types.

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

Exile target creature. If its power is 3 or greater, return that card to the battlefield under its owner's control at the beginning of the next end step.

Mortal Realms enters tapped unless you control two or more other lands.
{T}: Add {R}.
{T}, Pay 1 life: Add {B} or {G}.

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.

When target creature you control dies this turn, create a token that's a copy of it, except it has no mana cost.

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
{3}: Unlock Mortal's Conundrum. If the revealed card is black, put it into your hand. Otherwise, put it on top of your library.
At the beginning of your upkeep, if Mortal's Conundrum is unlocked, you lose 2 life.

Mosecf, the Sunseeker's Path enters tapped.
Whenever a creature you control attacks, put a creation counter on Mosecf.
{T}, Remove ten creation counters from Mosecf and sacrifice it: Creatures you control get +2/+2 and gain vigilance until end of turn. Activate only as a sorcery.

Deathtouch

({T}: Add {B} or {G}.)
Mossy Shrine enters tapped unless you control two or more basic lands.

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

(Transform this if it's not attached to a creature. Pay {1}{W} as a sorcery to unattach it.)
Enchant creature you control
Mount of Heroes's rider gets +2/+1.
Sacrifice Mount of Heroes: Counter target spell that targets you or Mount of Heroes's rider.

(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.

Menace
At the beginning of your end step, Mountain Tyrant deals 1 damage to each creature you don't control.

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.

Target creature can't be blocked this turn.

Flash
Enchant creature
When Moved by Instinct enters, put a +1/+1 counter on enchanted creature.
Enchanted creature has haste and trample.

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

({T}: Add {U} or {B}.)
Muggy Mire enters tapped unless you control two or more basic lands.

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.)

Multipurpose Mannequin gets +1/+1 for each permanent attached to it.

As an additional cost to cast this spell, exile a creature card from your graveyard.
Create a tapped 2/3 black Mummy creature token.

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.