msem-instigator

Target creature gets +1/+0 for each land you control and gains trample until end of turn.
Orchestrate {1}{G} (You may exile this card from your hand anytime you could cast a sorcery for its orchestrate cost. When you next resolve a spell, you may cast this from exile without paying its mana cost.)

Flash
When Scholar of Necromancy enters, if a creature died this turn, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Flash
When Scholar of Reflections enters, you may switch target creature's power and toughness until end of turn.

Up to three target creatures each get +1/+1 until end of turn.

Add three mana of any one color.

When Scintillating Tome enters, choose a nonbasic card name.
{T}: Scry 1, then you may reveal the top card of your library. If a card with the chosen name is revealed this way, put it into your hand.

When Scion of Pestilence enters, create a black enchantment token named Blight with “At the beginning of your upkeep, you lose 1 life.”

Poisonous 2 (Whenever this creature deals combat damage to a player, that player gets two poison counters.)
Snakes you control can't be blocked by creatures with power 2 or less.

As Scion of Silence enters, choose a nonland card name.
Other permanents with the chosen name lose all abilities.

Vigilance
Other Knights and Soldiers you control get +1/+1.
{2}{B}, {T}, Sacrifice a Knight or Soldier: Destroy target creature or planeswalker. Activate only as a sorcery.

Sacrifice Scions of Old Jidai: Target player gains life equal to the life that player has lost this turn.

As an additional cost to cast Scorched-Earth Defence, reappropriate X times. (To reappropriate, exile exactly two cards from your hand and/or graveyard.)
Scorched-Earth Defence deals X damage to each creature and each planeswalker.

This spell can't be countered.
Players can't gain life.
{1}{R}: This enchantment becomes a 4/4 red Elemental creature with trample and haste until end of turn. Activate only during your turn.

Scorching Dragonfire deals 3 damage to target creature or planeswalker. If that permanent would die this turn, exile it instead.

Counter target spell with no subtypes. Surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)

Equipped creature gets +2/+2.
{1}: Attach Scoundrel's Aetherlock to target Rogue.
Equip {2}

Look at the top four cards of your library. You may put a land card from among them onto the battlefield tapped, then put the rest into your graveyard.

Target opponent reveals their hand. You choose a nonland card from it. That player exiles that card.
Each player conjures a card named Data-Point into their hand. (It's a sorcery that costs {2} with “Draw a card.”)

Embellish {3}{B} (If you cast this spell for {3}{B}, create a 1/1 blue Thopter artifact creature token with flying when it enters.)
When Scrap Spiral enters, target creature gets -2/-2 until end of turn.
{3}{B}, {T}, Sacrifice an artifact: Target creature gets -2/-2 until end of turn.

Vigilance, trample

Flying
Dragon spells and Adventure spells you cast cost {1} less to cast.

{3}{B}, Exile Screeching Duneborn from your graveyard: You gain 1 life and draw a card.

Whenever you cast a spell with mana value greater than Script Jockey's power, put a +1/+1 counter on Script Jockey.

As Scrolls of Succession enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.
{2}, {T}: Draw a card. Then discard a card unless you control three or more creatures of the chosen type.

Scrollsnatcher can't block and can't be blocked.
Whenever Scrollsnatcher deals combat damage to a player, look at the top card of each library, then put any number of those cards into their owner's graveyards.