msem-instigator

Search your library for a Plains, Island, Swamp, or Mountain card and put it onto the battlefield tapped. Then shuffle.

Each player mills three cards.
Draw a card.

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
Create a tapped colorless Mountain Forest land token. (It has “{T}: Add {R} or {G}.”)

Civilized — Whenever Founding Hero attacks, if you control an artifact, a creature, and an enchantment, Founding Hero gains double strike until end of turn.

You may put a creature or Revelation card from your hand onto the battlefield. Exile that permanent if it would leave the battlefield. If it's a Revelation, it enters the battlefield as a Horror creature.
Coalesce {7}{U}{U} (You may cast this from your graveyard for {7}{U}{U}. If you do, put it onto the battlefield as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Dead-Set Duo can't block.
Whenever Dead-Set Duo deals combat damage to a player, you may pay {B} and sacrifice it. If you do, they discard two cards.

Profane Emissary gets +2/+2 and has lifelink as long as you control a Demon.
If you would draw a card, you may instead search your library for a Demon card, reveal it, put it into your hand, then shuffle. You lose life equal to that card's mana value.

Menace
When Scion of Calamities enters the battlefield, exile the top two cards of your library. Until the end of your next turn, you may play one of those cards.
Whenever a Mountain enters the battlefield under your control, you may aetherize Scion of Calamities. (Create a token that's a copy of it, then exile that token.)

First strike
Other Foxes you control get +1/+1.
Whenever a Fox you control becomes blocked, it deals 1 damage to each creature blocking it.

Mill five cards. You may choose up to two nonland cards with mana value 2 or less milled this way. You may cast one without paying its mana cost. Put the rest into your hand.
Coalesce {6}{G}{W} (You may cast this from your graveyard for its coalesce cost. If you do, put it onto the battlefield as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
Flying, vigilance

Menace, haste
Whenever another player casts a spell that targets Plasma Addict, that player gains control of Plasma Addict.

Deception {U}{B} ({U}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Sacrifice a creature: Shinrei of the Ghosting Way can't be blocked this turn.
Whenever one or more Rogues you control deal combat damage to a player, return a creature card from your graveyard to your hand.

This spell can't be countered.
{R/G}: Target spell can't be countered.

Flying
When Cadre Hawk enters the battlefield, you may search your library and/or graveyard for a card named Cadre Hawk, reveal it, and put it into your hand. If you searched a library this way, shuffle.

Enchant creature
You control enchanted creature.
Enchanted creature gets +1/+1 and has slipstream. (This creature can't be blocked as long as only creatures with slipstream are attacking.)

Counter target instant or sorcery spell unless its controller pays {3}.

Target opponent chooses a card type, then reveals their hand. You choose a card from it that's not of the chosen type. That player discards that card.

Destroy target nonbasic land.
Abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)

(As you complete a condition, decode it. After all are decoded, you solve the mystery and transform this.)
When Mystery of the Crashed Craft enters the battlefield, create a 1/1 red Alien creature token.
{MAG}—You cast an instant spell.
{MAG}—You cast a sorcery spell.

Whenever you cast an instant or sorcery spell, create a 1/1 red Alien creature token.
{2}{R}, Sacrifice two Aliens: Copy target instant or sorcery spell you control. You may choose new targets for the copy.

Flash
If a spell or ability an opponent controls would cause you to discard a creature card, you may put that card onto the battlefield instead.

You may play an additional land on each of your turns.
Whenever Antali Archdruid attacks, if two or more lands entered the battlefield under your control this turn, Antali Archdruid deals 3 damage to any target and you gain 3 life.

Flash
TT-23 Aegis can't attack or block unless you have six or more cards in hand.
At the beginning of your end step, if you didn't cast a spell this turn, draw a card.

Constructs you control have haste.
When Urak, Voice of the Horde or another Construct enters the battlefield under your control, creatures you control get +1/+0 until end of turn.
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

Target player mills X cards, where X is the number of cards in your graveyard.
Flashback {3}{U/B}{U/B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)