msem-instigator

(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.
{MG} — You cast an instant spell.
{MG} — You cast a sorcery spell.

{R}, Sacrifice Nacatl Skirmisher: Destroy target artifact.
Stampede — Whenever Nacatl Skirmisher and a creature with greater power attack, creatures you control get +1/+0 until end of turn.

Destroy target artifact or enchantment. Its controller gains 4 life.

As Nebula of Empty Gold enters the battlefield, choose two or more colors. You lose life equal to the number of colors chosen this way.
{T}: Add one mana of any of the chosen colors.

Counter target noncreature spell.

{T}: Add {C}.
Wanderlust — {6}, {T}: Draw two cards. Activate only if you control four or more differently named lands.

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

As New Divide enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.
{T}, Sacrifice New Divide: Search your library for a basic land card, put it onto the battlefield, then shuffle.

When Ninhasir's March enters the battlefield, it deals 3 damage to any target.
{1}{R}{R}: Transform Ninhasir's March. Activate only if your fealty to Mountains is five or greater.

You may return a land you control to its owner's hand rather than pay this spell's mana cost.
Northern Express Line enters the battlefield tapped.
{T}: Add {U}.

As Ocean Monastery enters the battlefield, you may pay 2 life. If you don't, Ocean Monastery enters the battlefield tapped.
{T}, Sacrifice Ocean Monastery: Search your library for a Plains or Island card, put it onto the battlefield, then shuffle.

This spell costs {G} less to cast if it targets a blue or black permanent.
Destroy target artifact, enchantment, or planeswalker.

Search your library for a basic land card, reveal it, put it into your hand, then shuffle. Scry 2.

Each player mills three cards.
Draw a card.

When Ostracizer Orb enters the battlefield, exile target nonartifact, nonland permanent until Ostracizer Orb leaves the battlefield.

Exile target creature. That creature's controller creates a 1/1 blue Elemental creature token with flying.

{T}: Add {C}.
{T}, Pay 1 life: Add {R}.
{4}{R}, {T}, Sacrifice Path of Fire: Path of Fire deals 3 damage to target player or planeswalker. Activate only as a sorcery.

Target opponent reveals their hand. You choose a nonland card from it. If you can't, they discard a card. Otherwise, that player discards a card, then if they didn't discard the chosen card, you create a tapped Treasure token.

Changeling (This card is every creature type.)
{T}: Add {C}.

({T}: Add {W} or {U}.)
Pool of Light enters the battlefield tapped unless you control a basic Plains or a basic Island.

Counter target spell unless its controller pays {2}.
Wanderlust — If that spell has mana value 2 or less and you control four or more differently named lands, counter that spell.

Flash
Flying
When Powder Scatterer enters the battlefield, exile target noncreature spell. Its controller draws a card.

Flash
Flying
Prodigious Panya has base power and toughness 4/4 during extra turns.

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.

Target player reveals their hand. You choose a nonland card from it. That player discards that card. You lose 1 life.
Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)