msem-instigator

(As you complete a condition, decode it. After all are decoded, you solve the mystery and transform it.)
When Mystery of the Dying Herds enters, create a 0/2 white Ox creature token.
A creature you control dies.
You have 4 or more life than your starting life total.

When Mystic Mackerel enters, you may have target player mill two cards.
{3}{U}, Sacrifice Mystic Mackerel: Return target enchantment, instant, or sorcery card from your graveyard to your hand.

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

{2}{U}, Sacrifice Nameless Drifter: Draw a card for each creature that left the battlefield this turn.

Return target creature you control to its owner's hand. You gain life equal to its power.

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

Put a +1/+1 counter on target creature.
Flashback {1}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Defender (This creature can't attack.)
When Naturebound Druid enters, you may search your library for a basic land card, reveal it, then shuffle and put that card on top.

Flying
{2}{U}, {T}: Target creature gets +1/+1 and gains flying until end of turn. Activate only as a sorcery.

Exile target permanent you control, then return that card to the battlefield under your control.

Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
Add one mana of any color.

Deathtouch
When Nel Toth Shaman enters, mill two cards.

Whenever Neo-Soul Attendant or another enchantment you control enters, you gain 1 life.

Whenever Netsight Trickster deals combat damage to an opponent, create a Function token with “Draw a card. Then discard a card unless you pay {2}.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

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

Return target creature card from your graveyard to your hand. If that card is a Human, you gain 3 life.
Flashback {3}{W} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Harmony — You gain 2 life.
When New Alores Fiddler enters, harmonize. (Trigger up to one harmony of one permanent you control.)

Create a 1/1 white and black Badger Cleric creature token with lifelink. (Then exile this card. You may cast the creature later from exile.)

Menace
Ni'Ama's Emissary gets +1/+1 as long as you control a red or white permanent.

Nimblefoot can't be blocked.

Flying
{3}{U}, Sacrifice Nimbus Fae: Put target creature on top of its owner's library.

Flying
Sacrifice Nimbus Glider: Creatures you control gain flying until end of turn.

Nip at the Heel deals 1 damage to any target. Create a 1/1 red Hound creature token.

When Nitrous Renewer enters, you may put a land card from your hand onto the battlefield tapped.
{3}{G}, Exile Nitrous Renewer from your graveyard: Return target land card from your graveyard to your hand. Activate only as a sorcery.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
At the beginning of your end step, if you've cast three or more spells this turn and Nizev Enforcer isn't a token, create a token that's a copy of it.