msem-instigator

{T}, Sacrifice a creature: Target player discards a card and loses 1 life. Activate only as a sorcery.

({T}: Add {B}.)
Wanderlust — Otherworldly Swamp enters tapped unless you control four or more other differently named lands.
{1}, {T}: Add one mana of any color.

Mechanized Ideal gets +X/+Y, where X is the highest base power among other creatures you control and Y is the highest base toughness among other creatures you control.

Whenever one or more cards are put into exile from anywhere, target opponent loses 1 life.
Whenever one or more creatures you control deal combat damage to a player, you may pay 2 life. If you do, purge. (Exile two cards that share a type from graveyards. If you do, draw a card.)

Trial 4 (As you cast this spell, an opponent of your choice may pay 4 life. If they don't, they fail the trial.)
Target player sacrifices two noncreature permanents if they failed the trial.

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.”)

Menace
Whenever an opponent activates an ability that isn't a mana ability, Flensing Tormentor deals 1 damage to that player.

Scry 2. (Then exile this card. You may cast the creature later from exile.)

Target creature you control deals damage equal to its power to target creature you don't control.
Whenever a creature you control with deathtouch deals damage to an opponent, you may sacrifice that creature. If you do, return Shedding of the Coils from your graveyard to your hand.

{U}: Aqueous Treader gets +1/-1 until end of turn.
{U}: Aqueous Treader gets -1/+1 until end of turn.

When Lotus Debutante enters, create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”
{3}{U}: Draw a card.

Whenever you cast a spell that's white, blue, black, or green, put a +1/+1 counter on Hesitant Vanguard.
Surpass {5}{R} ({5}{R}: Transform this creature. This costs {1} less to activate for each counter on it. Activate only as a sorcery.)

As Alratha, Pearl of the Sand Sea enters, you may have an opponent investigate. If you don't, it enters tapped.
{T}: Add {U}.
{1}{U}, {T}: Investigate.

At the beginning of your upkeep, mill a card.
Whenever a creature card is put into your graveyard from anywhere, if that card has flying, you may put a flying counter on Berylscale Alaj. Repeat this process for first strike, double strike, deathtouch, hexproof, lifelink, menace, reach, trample, and vigilance.

When Rhudai Overseer enters, look at the top four cards of your library. You may reveal an artifact or enchantment card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Each player mills three cards. For each instant and/or sorcery card milled this way, draw a card.

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Target opponent mills three cards.
III — You may cast target nonland card from a graveyard this turn and you may spend blue mana as though it were mana of any color to cast it.

Target creature gets +2/+1 and gains trample until end of turn.

Insightful Blow deals 3 damage to target attacking or blocking creature. Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Cast this spell only during your turn and only during the declare attackers step or with its acquiesce ability.
Untap all creatures you control. After this phase, there is an additional combat phase.
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

Each player discards their hand and sacrifices five lands. Cinders of an Old Era deals 5 damage to each creature and planeswalker.
At the beginning of each player's next first main phase, that player draws seven cards and adds five mana in any combination of colors.

Vigilance (Attacking doesn't cause this creature to tap.)

When Fish Out of Water enters, exile the top four cards of each library.
During each of your turns, you may cast a card exiled with Fish Out of Water without paying its mana cost.

When Unity Spheres enters, create two 1/1 colorless Construct artifact creature tokens.
Tap two untapped creatures you control: Add two mana of any one color.