msem-instigator

At the beginning of your upkeep, you lose 1 life and create a 1/1 white Soldier creature token with melee. (Whenever that creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)

({T}: Add {G} or {U}.)
Secluded Cascade enters tapped unless you control two or more basic lands.

Exile target creature or planeswalker card from a graveyard. Search its controller's hand, graveyard, and library for any number of cards with the same name as that card and exile them. Then that player shuffles.

Sabotage — Whenever an opponent or permanent an opponent controls becomes the target of a spell you control, target creature you control can't be blocked this turn.
{B}{B}{B}: Secret Thief gets +3/+0 until end of turn.

Choose one or more —
• Target player draws two cards.
• Counter target spell.

({T}: Add {W} or {U}.)
Whenever Sedate Tundra becomes tapped, you lose 1 life unless you control two or more basic lands.

Whenever a creature you control enters, if it wasn't cast from your hand, you may mill a number of cards equal to its mana value. If you do, you may return a noncreature card milled this way from your graveyard to your hand.

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

“I was filled with fear, but looking across our great city, I know we will survive.”
I — Create a 0/4 white Wall creature token with defender.
II — Put a +1/+1 counter on up to one target creature.
III — Until your next turn, each creature you control assigns combat damage equal to its toughness rather than its power.

Take an extra turn after this one. During that extra turn, you may cast spells you own not named See the World from outside the game by tapping an untapped Scout you control in addition to paying their mana costs.
Exile See the World.

At the beginning of combat on each of your turns, you may have target land you control become a 3/3 Elemental creature with haste until end of turn. It's still a land.
Sacrifice Seeds of New Life: Return up to two target land cards from your graveyard to your hand. Activate only as a sorcery.

({T}: Add {G}.)
Seedshrine enters tapped.
When Seedshrine enters, you may put a +1/+1 counter on target creature.

{T}, Pay 1 life: Add {B} or {G}.
{1}, {T}, Sacrifice Seedy Bar: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Whenever you draw a card, put a quest counter on Seek Perfection.
At the beginning of each end step, if Seek Perfection has four or more quest counters on it, exile target permanent you control, then return it to the battlefield under your control.

Reveal the top three cards of your library. Put one into your hand and the rest on the bottom of your library in any order.

Look at the top five cards of your library. You may reveal a creature card or a land card from among them and put it into your hand. Put the rest into your graveyard.
Abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)

At the beginning of your upkeep, you gain 1 life. Then if your life total is greater than or equal to your starting life total, you gain an additional 1 life and scry 1. Then if your life total is greater than or equal to three times your starting life total, you win the game.

Scry 2, then draw two cards.
You have no maximum hand size for the rest of the game.

(Add a quest counter as this enters. Sacrifice after 3.)
Whenever you attack, add a quest counter.
Create a 0/1 white Human creature token named Lost Child.
Scry 2.
Exile a token you control named Lost Child. If you do, create two 1/1 white Soldier creature tokens and you gain 4 life.

Whenever you play a land, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
{1}{G}{U}{R}, Sacrifice three Clues: Exile cards from the top of your library until you exile three nonland cards. You may cast any number of those cards without paying their mana costs.

As long as a creature you control has flying, creatures you control have flying. The same is true for first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance.

Whenever Seeker of Battle attacks, put a +1/+1 counter on each creature you control. Those creatures gain trample until end of turn.

When Seeker of Horizons enters, reveal the top three cards of your library. You may put a permanent card from among them into your hand. Put the rest on the bottom of your library in any order.
Recite {1}{U} (You may cast this creature from your graveyard for its recite cost. If you do, exile it when it enters or if it would leave the battlefield.)

Lifelink
When Seeker of Lost Secrets leaves the battlefield, you may pay 2 life. If you do, search your library for a card, put that card into your hand, then shuffle.

Flying
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)