msem-instigator

Improve {1}{G/U} ({1}{G/U}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
You may play an additional land on each of your turns.
Wanderlust — At the beginning of your end step, if you control four or more differently named lands, you may draw a card.

Flying, haste
{X}{R}{R}, Exile an instant or sorcery card with mana value X from your graveyard: Return Merkurio's Familiar from your graveyard to the battlefield. It gets +X/+0 until end of turn.

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.

Equipped creature gets +2/+1.
Whenever a creature you control deals combat damage to a player or planeswalker, you may attach Mervin's Armor to it.
Equip {4}

Survivors you control get +3/+3.

Equipped creature gets +0/+4.
Equip {2}

Choose one —
• Destroy target artifact.
• Metal Munch deals 1 damage to each of up to two targets.

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.

{3}{R}: Attacking creatures you control get +1/+0 until end of turn.

{T}: Add one mana of color.
{3}{G}, {T}: Audition for green. Activate only as a sorcery. (Create a 1/1 Construct Actor creature token, a Scout Role giving 2/3 and vigilance, or a Warrior Role giving 3/2 and trample. Roles replace older ones.)

Harness (You may tap a creature you control as you cast this spell. If you do, reduce this spell's mana cost by that creature's power.)
Exile the top three cards of your library. Cast a spell with mana value X or less from among them without paying its mana cost.

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.)

Engage (This creature must be blocked each combat if able.)
{R}: Mettlesome Watchkeeper gets +1/+0 until end of turn.

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.

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.

({T}: Add {B}.)
As Midnight Gate enters, you may pay 1 life. If you don't, Midnight Gate enters tapped.
Basic lands you control have “{T}: Add {B}.”

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

Flash

{T}, Mill a card: Add {G}.
{X}{U}{B}, {T}, Exile a permanent card with mana value X from your graveyard: Create a tapped token that's a copy of it, except it's an X/X Elemental creature in addition to its other types.