msem-instigator

Draw three cards.
Reprise {5}{U}{U} (As you cast an instant or sorcery spell, you may exile one card with reprise from your graveyard and pay its reprise cost. If you do, add its effects to that spell.)

Kicker {2} (You may pay an additional {2} as you cast this spell.)
Prowess
When Merkurio's Opus enters, if it was kicked, draw two cards, then discard two cards.

Counter target spell unless its controller pays {2} for each Wizard on the battlefield.

Return target nonland permanent to its owner's hand.
Reprise {2}{U} (As you cast an instant or sorcery spell, you may exile one card with reprise from your graveyard and pay its reprise cost. If you do, add its effects to that spell.)

[+1]: The next instant or sorcery spell you cast this turn costs {1} less to cast.
[–4]: Until end of turn, whenever you cast an instant or sorcery spell, Merkurio deals 2 damage to any target.
[–8]: Exile the top seven cards of your library. You may cast any number of instant and sorcery cards from among them without paying their mana costs.

Motivate 1 (When this creature enters, you may motivate target creature with less power than this by putting a +1/+1 counter on it.)
When Merthilios' Escort motivates a creature, that creature gains first strike until end of turn.

Survivors you control get +3/+3.

Enchant creature
When Mesmerizing Shimmer enters, untap enchanted creature. It gains haste until end of turn.
You control enchanted creature.
Mirage {2}{U}{R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

I, II — Target creature you control gets +2/+0 and gains menace until end of turn.
Discovery — Attacking creatures you control get +2/+0 and have menace.

Whenever another artifact you control enters, put a +1/+1 counter on Metalwork Machinist.

Choose one —
• Meteor Fall deals 4 damage to each creature and each planeswalker.
• Meteor Fall deals 8 damage to target creature or planeswalker.

When Meteor Harbinger enters, choose one —
• Meteor Harbinger deals 2 damage to each creature.
• Each player sacrifices two lands.
• Meteor Harbinger deals 2 damage to each of two target players or planeswalkers.

Meteor Volley deals 3 damage to each creature.
Reprise {4}{R}{R} (As you cast an instant or sorcery spell, you may exile one card with reprise from your graveyard and pay its reprise cost. If you do, add its effects to that spell.)

Meteorain deals 5 damage divided as you choose among any number of target creatures or planeswalkers.

Artifact spells you cast cost {1} less to cast.
{2}, Sacrifice an artifact: Target creature gains deathtouch until end of turn.

Embellish {4}{W} (If you cast this spell for {4}{W}, create a 1/1 blue Thopter artifact creature token with flying when it enters.)
When Meticulous Mechanist enters, scry 1.

Enchant creature or artifact
When Meticulous Process enters, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
Enchanted permanent doesn't untap during its controller's untap step.

When Mettalia's Forward enters, you may salvage a card. (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.)

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.)

Whenever a land you control enters, crystallize.
{10}: Shuffle any number of other permanents you control into their owner's library. Mill that many cards. Put all permanent cards milled this way onto the battlefield. Activate only during your turn and only once each turn.

Mianju enters with your choice of a menace or +1/+1 counter on them.
Whenever two or more creatures in Mianju's pack attack, mill three cards, then return a creature card from your graveyard to your hand. (Two or more creatures you control with equal power are in a pack.)

Create a 2/2 blue Jellyfish enchantment creature token with flying.
Flashback {4}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

When Miasma Spewer enters, you may sacrifice a permanent. When you do, Miasma Spewer deals 1 damage to each opponent and each creature and planeswalker they control.

Whenever you discard a card, choose up to one that hasn't been chosen this turn —
• Draw a card.
• Tap target creature. Put a stun counter on it.
• Create a 2/2 blue Jellyfish enchantment creature token with flying.

Flash
Wanderlust — When Microzoologist enters, search your library for a creature card with mana value 1. If you control four or more differently named lands, you may search for a creature card with mana value 3 or less instead. Reveal that card, put it into your hand, then shuffle.