msem-instigator

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

Merciless Champion can't block unless you control another Knight or Soldier.

Infiltrate (Whenever one or more attacking creatures you control aren't blocked, this creature gets +1/+1 until end of turn.)
Whenever Merciless Exiled deals combat damage to a player, scry 2.

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.

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.”

Menace
Ferocious — Whenever Merciless Xun Huang attacks, if you control a creature with power 4 or greater, defending player sacrifices a permanent.

{2}{G/U}{G/U}, {T}: Untap each non-Lizard permanent you control.

{1}{U}: Mercurial Merfolk gets +2/-2 until end of turn.
When Mercurial Merfolk dies, draw a card.

This spell can't be countered.
Whenever Meren, Bane of the Cairns attacks, exile target creature card from your graveyard. You may cast that card for as long as it remains exiled by sacrificing a creature in addition to paying its other costs.

{T}: Draw a card, then discard a card.

Whenever Merfolk Vandal deals combat damage to a player, you may pay {U}. If you do, transform it.

Whenever Merfolk Visionary or another Merfolk creature you control enters, scry 2. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Skip your draw step.
At the beginning of your upkeep, shuffle your hand and graveyard into your library, then draw three cards.
You can't cast more than one spell each turn.

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.

[+1]: Merkurio deals 2 damage to target player or planeswalker. That player or that planeswalker's controller may draw a card.
[–2]: The next instant or sorcery spell you cast this turn costs {U}{R} less to cast. This effect reduces only the amount of colored mana you pay.
[–7]: You get an emblem with “Each instant and sorcery card you own has reverberate {X}, where X is its mana value.” (When you cast a spell, copy it if you paid its reverberate cost. You may choose new targets for the copy.)

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.

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.

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.

Whenever Merrow Legendmaker attacks, look at the top five cards of your library. You may reveal an Aura, Aurashaper, or Equipment card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

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.