msem-instigator

Ride {2}{W} ({2}{W}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Flying, haste
Whenever Ma'Long deals combat damage to a player, draw a card, then add that much mana in any combination of {U} and/or {R}. Until end of turn, you don't lose this mana as steps and phases end.
Instant and sorcery cards in your hand have showcase. The showcase cost is equal to the card's mana cost plus {2}. (If you cast it for its showcase cost, create a 1/1 red Bard creature token that can't block and exile that card. Whenever the Bard attacks, you may cast a free copy of the exiled card.)

Create a tapped Treasure token.
Memento {2}{B}{B} (You may cast this from your graveyard for {2}{B}{B}. If you do, put it onto the battlefield transformed after it resolves. Exile it if it would leave the battlefield or not resolve.)

Whenever you gain life for the first time each turn, reveal the top card of your library. If it's a land or creature card, put it into your hand. Otherwise, put it into your graveyard.

If Madame Beatrice would leave the battlefield, exile her instead.
Whenever one or more creatures you control deal combat damage to a player, that player reveals their hand. You may cast a card from their hand without paying its mana cost.

Indestructible
Whenever this creature enters the battlefield or transforms into Mahara, recruit. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)
At the beginning of your end step, if you control four or more creatures, transform Mahara.

Flying, lifelink
Your opponents can't search libraries.
{B}, Pay 2 life, Discard a card: Search your library for a card, then shuffle and put that card on top.

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.

Flying
Whenever you tap a land for mana, add one mana of any type that land produced.
At the beginning of each end step, if you control no untapped lands, transform Martoob, Blessing of Water.

Whenever an Actor you control becomes untapped, you may discard a card. If you do, draw a card.

First strike
Mauling Mother gets +1/+1 for each other creature you control.

Flying
Whenever you cast a spell, draw a card, then put a +1/+1 counter on Maven of Perspective.

Lifelink
If a source would deal damage to a player, you may prevent X of that damage, where X is the number of +1/+1 counters on Mending Caretaker.

Whenever Merfolk Vandal deals combat damage to a player, you may pay {U}. If you do, transform it.

Players play with the top card of their libraries revealed.
[+2]: Target player mills a card. Draw a card.
[+1]: Create a 1/1 blue Illusion creature token with “This gets +1/+1 for each other Illusion you control.”
[–4]: Return target creature card from a graveyard to the battlefield under your control. It's an Illusion in addition to its other types.

Noncreature spells your opponents cast cost {1} more to cast.
Unveil {2}{W}{U} ({2}{W}{U}: Transform this. Unveil only as a sorcery.)

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Whenever Mistress of Frost extorts a spell, you may tap target artifact or creature.

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

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.

Whenever a land enters the battlefield under your control, put a +1/+1 counter on Mountain Runt, then it deals 1 damage to up to one target creature you don't control.
When Mountain Runt has three or more +1/+1 counters on it, remove them all and transform it.

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

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

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.)