msem-instigator

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

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

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.

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}

Flying
When Messenger of the Heavens enters, surveil 1.
Whenever Messenger of the Heavens deals combat damage to a player, exile any number of target creatures in its pack, then return them to the battlefield under your control. (Two or more creatures you control with equal power are in a pack.)

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

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

({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.

Ferocious — Whenever a creature with power 4 or greater you control enters, Mieng, Who Dances With Dragons becomes a 4/4 Dragon creature with flying until end of turn.

Target attacking creature gets +3/+0 until end of turn.

When Mighty Totem enters, scry 1.
{1}{G}, Sacrifice Mighty Totem: Target creature gets +3/+3 until end of turn.

MiliCore Barracks enters tapped.
{T}: Add {B} or {R}.
{B}{R}, {T}: Create a Function token with “Deathtouch.” Activate only if an opponent lost life this turn. (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Whenever you gain life, Militant Youth gets +1/+1 until end of turn.

Flash
You may cast the first spell that's an enchantment, instant, or sorcery with mana value 1 you cast each turn without paying its mana cost.

Enchant player
Enchanted player's maximum hand size is reduced by two.

Mind Palace enters tapped.
{T}: Add {U} or {B}.
When Mind Palace enters, you may put a loyalty counter on a planeswalker you control.

Equipped creature gets +1/+1. If it's a token, it gets +3/+3 instead.
Equip {2}

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
When the fourth spell of a turn is cast, you may unlock Mirror Cipher. If the revealed card is an instant or sorcery card, cast it without paying its mana cost and copy it. You may choose new targets for the copy.

Whenever equipped creature blocks or becomes blocked by a creature, you may have equipped creature become a copy of that creature until end of turn.
Equip {1}

Mirrorgate enters tapped.
When Mirrorgate enters, you choose a nonbasic land card name other than Mirrorgate, then each player chooses a color.
Lands with the chosen name are lands with “{T}: Add one mana of any of the chosen colors,” and lose all other abilities, card types, and land types.
{T}: Add one mana of any of the chosen colors.

When Miserable Portent enters, create a 1/1 black Harpy creature token with flying.
{3}{B}, Sacrifice Miserable Portent: You draw two cards and you lose 2 life.

Create a 1/1 blue Illusion creature token with “This gets +1/+1 for each other Illusion you control.”
Coalesce {6}{B} (You may cast this from your graveyard for {6}{B}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
Misery Keeps Company is an Illusion in addition to its other types while it's a creature.

Players play with the top card of their libraries revealed.
[+2]: Target player mills a card. Draw a card.
[+1]: Create a 1/1 blue Illusion creature token with “This gets +1/+1 for each other Illusion you control.”
[–4]: Return target creature card from a graveyard to the battlefield under your control. It's an Illusion in addition to its other types.

Counter target noncreature spell with an odd mana value. (Zero is even.)