msem-instigator

Flash
Flying
When Mending Valkyrie enters, choose target permanent you own or permanent card with mana value 3 or less in your graveyard. You may return it to your hand.

Other Elementals you control get +2/+2.
Whenever one or more Elementals you control attack, tap up to one target creature you don't control.

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Whenever one or more creatures deal combat damage to you, exile one of those creatures.
You may cast cards exiled with Merciless Mirror and may spend mana as though it were mana of any color to cast those spells.

This spell costs {1} less to cast if you control a Warrior.

Choose two —
• Counter target spell unless its controller pays {6}.
• Target player draws two cards, then discards a card.
• Creatures target player doesn't control get -3/-0 until end of turn.
• Exile up to two target creatures, then return those cards to the battlefield under their owners' control.

[+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.

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.)

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

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
Mighty Xioshu can't be blocked by creatures with power 2 or less as long as you're in a renaissance.

Target player reveals their hand. You choose three cards from it and exile them. Then that player exiles the top three cards of their library.

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever Mindscreech Drake deals combat damage to a player, that player mills three cards.

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

Flying, ward {2}
At the beginning of your upkeep, if Mirrorwing Commander is embattled, create a token that's a copy of it. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Flash (You may cast this spell any time you could cast an instant.)
When Mist Lurker enters, tap all creatures you don't control.

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

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.)

Vigilance
{7}{G}: Molting Linnorm gets +5/+5 and gains trample until end of turn.

{W}{U}, {T}: Target creature gets +2/+2 and gains flying until end of turn.
{U}{B}, {T}: Target player mills three cards.
{B}{R}, {T}: Monolith of Ages deals 3 damage to any target.
{R}{G}, {T}: Target creature gets +4/+2 and gains trample until end of turn.
{G}{W}, {T}: Populate. (Create a token that's a copy of a creature token you control.)

Exile target creature. That creature's controller reveals cards from the top of their library until they reveal a creature card. That player puts that card onto the battlefield, then shuffles the rest into their library. If you own that card, it enters with an additional X +1/+1 counters on it, where X is its power.

Assault {2}{R} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
When Monstrous Hila assaults, it deals 3 damage to any target.

When Monstrous Hunter enters, destroy up to one target creature.
At the beginning of each end step, if a creature died this turn, you draw a card and you lose 1 life.

Monumental Siege deals 5 damage divided as you choose among any number of targets. Whenever a creature dealt damage this way this turn dies, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)

Flying
Whenever another creature you control attacks, you may pay {1}. If you do, put a +1/+1 counter on it.

Codex — Leyran Alpha; Fungal Whomper; Plated Crusher; Towering Hydraffe; The Terror of Shady Cove. (As this enters, conjure its contents into a shuffled face-up additional library.)
When Mother of Monsters enters, you gain 6 life.
When Mother of Monsters dies, draw a card.