msem-instigator

Whenever Masha's Vanguard deals damage to a player, you may put a creature card with mana value X or less from your hand onto the battlefield, where X is the amount of damage dealt this way.

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Masked Lancer has first strike as long as it's attacking.
Whenever Masked Lancer mentors a creature, that creature gains first strike until end of turn.

Whenever a permanent you control leaves the battlefield, discard a card, then draw a card.
{1}{R}, Sacrifice a permanent: Mass Pandemonium deals 1 damage to any target.

Whenever an Actor you control becomes untapped, you may discard a card. If you do, draw a card.

Whenever a nonbasic nontoken land enters under an opponent's control, create a tapped colorless land token named Fading Rift with “{T}, Sacrifice this land: Add one mana of any color.”

Whenever an artifact you control enters, Master of Munitions deals 1 damage to each opponent.

Trample
Disgraced 2 (This enters with two -1/-1 counters. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)
Whenever a creature an opponent controls blocks, Master of No Quarter deals 2 damage to that creature.

Equipment spells you cast cost {1} less to cast.
Equip abilities you activate cost {1} less.

Wu Xing (Add effects based on the number of colors of mana spent to cast this spell.)
1 | When you next cast an instant or sorcery spell this turn, copy it. You may choose new targets for the copy.
3 | When you cast your next creature spell this turn, copy it.

When you cast this spell from anywhere other than your hand, it deals 5 damage to any target.
Trample

Your opponents can't gain life.
If a source you control would deal damage to an opponent, it deals double that damage instead.
At the beginning of your end step, if Mayhem Tandem didn't attack this turn, transform it.

Destroy target artifact.
Catalyze. (The next spell you cast this turn costs {1} less to cast.)

Enchant creature
When Melt the Chains enters, exile the top two cards of your library. Until the end of your next turn, you may play those cards.
Enchanted creature gets +3/+0.

Melt the Earth deals 2 damage to each creature.

Melting Point deals 2 damage to any target.

Enchant creature
Enchanted creature gets +1/+0.
Whenever enchanted creature attacks, target creature can't block this turn.

[+1]: Exile the top two cards of your library. You may play up to one card exiled this way this turn.
[–2]: Menna Al-Mejjat deals 3 damage to target creature. If that creature would die this turn, exile it instead.
[–6]: Draw cards equal to the number of cards in exile. Menna Al-Mejjat deals that much damage to any target.

Equipped creature gets +2/+0 and has haste.
Equip {2}

Armed — Merciless Brute gets +2/+2 as long as it's equipped.

Whenever Merciless Shieldbreaker enters or attacks, target opponent puts three rust counters on a permanent they control with no rust counters on it. That permanent gains “At the beginning of your upkeep, remove a rust counter from this permanent. Then if there are no rust counters on this permanent, sacrifice it and it deals 4 damage to you.”

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}

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.