msem-instigator

Flash
Enchant instant or sorcery spell
Enchanted spell's text box is “This spell deals 3 damage to you.”
{4}{U}{U}{R}{R}: Return Mental Meltdown from your graveyard to the battlefield.

When Mental Supremacist enters, choose target creature you don't control. That creature has base power and toughness 1/1 and loses all abilities for as long as you control Mental Supremacist.

Until end of turn, you may play cards you don't own from exile. Scry 1.

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.

Whenever another creature with power 4 or greater you control enters, you may draw a card.

Activated abilities you control cost up to {1} less to activate. This effect can't reduce the amount of mana an ability costs to activate to less than one mana.

Menace

Enchant opponent
Whenever a creature enters under enchanted player's control, that creature gets -0/-2 until end of turn unless that player pays 2 life.

As Mercantile Accords enters, choose a number.
Whenever an opponent casts a spell with the chosen mana value, you draw a card and create a Treasure token.

{T}: Add {C}.
Satrapies you control enter untapped.

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Mercenary Coercer deals combat damage to a player, that player discards a card.

Adorned — Mercenary Lancer gets +2/+2 as long as it's equipped and/or enchanted.

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
{2}{B}, Discard a card: Mercenary of the Folded Fan gains indestructible until end of turn. Tap it. If you're in a renaissance, draw a card.

Crew 3 (Tap any number of creatures you control with total power 3 or greater: This Vehicle becomes an artifact creature until end of turn.)

Deathtouch
Sacrifice a creature: Target player mills two cards.

Whenever Merchant of Flesh or another creature you control dies, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
{B}, Sacrifice two Treasures: Each opponent sacrifices a creature.

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

{T}, Sacrifice Merchant's District: Search your library for an Island or Mountain card and put it onto the battlefield tapped, then shuffle.

Draw three cards, then put two cards from your hand on top of your library in any order.

At the beginning of your upkeep, draw a card.
At the beginning of your end step, discard a card.

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

Flying, vigilance

Flying, vigilance
Prevent all damage Merciful Yuroda would deal to creatures.

Whenever Merciless Bandit or another creature you control dies, each opponent loses 1 life and you gain 1 life.

When Merciless Blackguard enters, each player sacrifices a creature. For each creature token sacrificed this way, you may create a Treasure token.