msem-instigator

Mettalia is all colors.
Mettalia has protection from each color among cards she's salvaged in exile.
When Mettalia enters, for each color, you may salvage a nonlegendary card of that color. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

{T}: Add {C}.
{3}: Mill two cards, then return Midnight Keep from your graveyard to the battlefield tapped.

As Mind-Mute enters, choose a card name.
Activated abilities of sources with the chosen name can't be activated unless they're mana abilities.
{5}: Return Mind-Mute to its owner's hand.

Creatures with power greater than the number of cards in their controller's hand can't attack.

When Mindwave Rod enters, attach it to target creature you control.
Equipped creature gets +1/+1 and has “Whenever this creature deals combat damage to a player, draw a card.”
Equip {2}

Flying
When Mineral Retriever enters, create a Treasure token.

Equipped creature gets +1/+1. If it's a token, it gets +3/+3 instead.
Equip {2}

At the beginning of your upkeep, choose another planeswalker you control. You may activate that planeswalker's loyalty abilities twice this turn rather than only once.
[+2]: You may put a land card from your hand onto the battlefield. If you don't, each player draws a card.
[–2]: Exile target permanent. Return it to the battlefield under its owner's control at the beginning of the next end step.
[–7]: For each land on the battlefield, add one mana of any type that land could produce.

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.

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}

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.

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

{T}: Add {C}.
{4}: Put a +1/+1 counter on Monument of Queens. You may have it become a 0/0 Avatar creature with flying, first strike, vigilance, trample, and lifelink until end of turn. It's still a land.

{5}, {T}, Exile a creature you control: Exile target creature.

Whenever a creature you control enters, put a devotion counter on Monument of the Masses.
At the beginning of your upkeep, if Monument of the Masses has thirty-five or more devotion counters on it, you win the game.

{T}: You may put a creature card with mana value 2 from your hand onto the battlefield.

Whenever Moonlit Lurker blocks, put a +1/+1 counter on it.

(Spend a different color of mana on each {VP}.)
Moresso, Infuser of Light is all colors.
Hexproof from monocolored
Whenever you cast a spell with four or more mana symbols in its mana cost, add four mana of different colors. This ability triggers only once each turn.

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

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

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

Whenever a creature with flying attacks you, gain control of that creature at end of combat.