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.

Whenever a player casts a spell, put a doom counter on Foreboding Presence.
At the beginning of each player's end step, if no spells were cast this turn, sacrifice Foreboding Presence. It deals damage equal to the number of doom counters on it to that player.

{2}, {T}: Target opponent exiles a nonland, nontoken permanent they control.
{2}, {T}: Put target permanent card exiled with Harmony Array onto the battlefield under your control.

When Dunesea Merchant enters, tap up to X target creatures, where X is the number of Satrapies you control.
Satrapycycling {2} ({2}, Discard this card: Search your library for a Satrapy card, reveal it, put it into your hand, then shuffle.)

If you control an Angel, Demon, Faerie, or Spirit, draw a card.
Exile target nonland permanent. Return that card to the battlefield under its owner's control at the beginning of the next end step.

Exile any number of target creatures. For each creature exiled this way, its controller creates a 3/2 green Crocodile creature token with trample.

{1}, {T}, Move a -1/-1 counter from another creature onto Grace of the Trinity: Another target creature gains indestructible until end of turn.

Smiting Helix deals 3 damage to any target and you gain 3 life.
Flashback {R}{W} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Flying
Whenever an opponent discards a card, put a +1/+1 counter on Nightbane Specter.
Whenever Nightbane Specter deals combat damage to a player, that player discards a card.

Whenever Agent of Vitu-Ghazi deals combat damage to a player, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Exile each player's graveyard. Create a token that's a copy of a creature card exiled this way.
II — Create a token that's a copy of an artifact or enchantment card exiled with Around the Plane in Three Days.
III — Create a token that's a copy of a land or planeswalker card exiled with Around the Plane in Three Days.

Lush Outskirts enters tapped.
{T}: Add {G} or {U}.
{3}{G}{U}: Until end of turn, Lush Outskirts becomes a 5/7 green and blue Plant creature with with ward {3} and “Whenever this creature attacks or blocks, torment yourself.” It's still a land. (To torment yourself, lose 3 life unless you discard a card or sacrifice a nonland permanent.)

Audition for white. If you create a Role this way, untap the creature it enchants. (Create a 1/1 Construct Actor creature token, a Scout Role giving 2/3 and vigilance, or a Cleric Role giving 2/2 and lifelink. Roles replace older ones.)

When Isle Conservator enters, if you control a legendary creature, submerge target creature an opponent controls. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

Return up to two target creature cards from your graveyard to your hand. If you control a creature with power greater than its base power, you gain 3 life.

When Shifty Squirrel enters, you gain 3 life.
Sacrifice a creature: Transform Shifty Squirrel.

Constructed Jay is all colors.
Constructed Jay gets +1/+0 and has flying as long as you control three or more Satrapies.

Put a +1/+1 counter on target creature you control if it's enchanted or equipped. It deals damage equal to its power to up to one other target creature.

When Viking Greataxe enters, attach it to target creature you control.
Equipped creature gets +2/+1.
Equip {3}

Captain Fina Redtail can't be blocked as long as you control another attacking Pirate.
Whenever Captain Fina Redtail deals combat damage to a player, you may pay {2}. If you do, create a 2/1 black and red Cat Pirate creature token with menace.

Nightwatch Rallier enters with X +1/+1 counters on it.
Other artifact creatures you control get +1/+1 for each +1/+1 counter on Nightwatch Rallier.

Clocktower Hideout enters tapped.
When Clocktower Hideout enters, look at the top card of your library. You may put it into your graveyard.
{T}: Add {B} or {R}.

{T}: Add {C}.
{3}{B}: Until end of turn, Tzhai's Throne becomes a 2/2 creature. It's still a land. It gets +2/+2 if {R} was spent to activate this ability, gets +2/+2 if {G} was spent, and gets +2/+2 if {W} was spent.

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)