msem-instigator

Reach
Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Other Elementals you control get +1/+1 as long as Miroran Skycatcher has a +1/+1 counter on it.

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.)
When the fourth spell of a turn is cast, you may unlock Mirror Cipher. If the revealed card is an instant or sorcery card, cast it without paying its mana cost and copy it. You may choose new targets for the copy.

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

When Mirror Paradigm enters, conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)
Once each turn, when a sorcery card is put into your graveyard from anywhere, you may copy it. If you do, you may cast the copy. (You still pay its costs.)

Sabotage — Whenever an opponent or permanent an opponent controls becomes the target of a spell you control, put a +1/+1 counter on Mirrorcast Battlemage.
Remove three +1/+1 counters from Mirrorcast Battlemage: Copy target instant or sorcery spell you control. You may choose new targets for the copy. Activate only once each turn.

Whenever equipped creature blocks or becomes blocked by a creature, you may have equipped creature become a copy of that creature until end of turn.
Equip {1}

Mirrorgate enters tapped.
When Mirrorgate enters, you choose a nonbasic land card name other than Mirrorgate, then each player chooses a color.
Lands with the chosen name are lands with “{T}: Add one mana of any of the chosen colors,” and lose all other abilities, card types, and land types.
{T}: Add one mana of any of the chosen colors.

The “legend rule” doesn't apply to artifacts and enchantments you control.
Equipped creature gets +1/+1 for each artifact and/or enchantment you control.
Equip {2}

Whenever you sacrifice a permanent, Mischievous Maolu gets +1/+1 until end of turn and you gain 1 life.

Other creatures you control get +2/+0 and have menace.
Whenever another creature you control dies, if it wasn't sacrificed, sacrifice a creature.

Glitch {2} (Remove one [restriction] for each time you pay the glitch cost.)
Create a 3/2 red creature token named Error with trample and haste. [Exile it at the beginning of the next end step.]

Hexproof
Mist-Valley Ancient enters tapped.
Cycling {2} ({2}, Discard this card: Draw a card.)

{1}{R}, Discard a card: Draw a card. Mist-Valley Minotaurs gets +2/+0 until end of turn.

Vigilance
Ignore all effects that would prevent Mistbreaker from attacking or blocking. (If an effect says it “can't” attack or block, it still can. This ability doesn't let it attack or block if it's tapped or attack if it has summoning sickness.)

Mistwake Hydra enters with X +1/+1 counters on it.
Creatures with power less than Mistwake Hydra's power can't block it.

Dragon spells you cast cost {1} less to cast.
{1}{R}: Until end of turn, Miyoga Dragonsoul becomes a 2/2 red Dragon creature with flying and “{R}: Miyoga Dragonsoul gets +1/+0 until end of turn.” Activate only as a sorcery.

Flying, haste
Miyoga Flameweaver can't block.
Whenever Miyoga Flameweaver attacks, exile the top card of your library. You may play that card until end of turn.

At the beginning of your upkeep, you may choose one —
• Put a card from your hand on the bottom of your library. If you do, draw a card.
• Discard a card. If you do, put the bottom card of your library into your hand.

Other creatures you control get +2/+2.

Modular Mercenary gets +1/+0 and has first strike as long as you control a creature with a +1/+1 counter on it.

First strike, haste
When Moeru Thunderers enters, if it's not a token, create a token that's a copy of it, except it has no mana cost.

Flash
When Mokuteki Ambusher enters, until end of turn, other creatures you control gain “{T}: This creature deals 1 damage to any target.”

Kicker {1}{G} (You may pay an additional {1}{G} as you cast this spell.)
When Mold Shambler enters, if it was kicked, destroy target noncreature permanent.

{T}: Add {G}.
Once during each of your turns, you may cast a creature spell from your graveyard if there are thirteen or more cards in your graveyard. (You still pay its costs. Timing rules still apply.)

This spell costs {1} less to cast for each card type among cards in your graveyard.
Trample