msem-instigator

{3}{B}: You mill two cards. Each opponent loses 2 life.
{1}{G}: You may put a land card from your hand or graveyard onto the battlefield tapped.

Target creature gets +3/+3 and gains trample until end of turn.

The next time one or more creatures you control would die this turn, exile those cards. You may play them until the end of your next turn.

Prowess
Whenever you cast a noncreature spell, you may choose target permanent with one or more time counters on it, then put a time counter on it or remove a time counter from it.

When Scaleblight Warrior enters, you gain 2 life.
Pay 2 life: Scaleblight Warrior gains menace until end of turn.

Enchant player
When Scaleblight's Quarry enters, you may have target creature you control deal damage equal to its power to target creature enchanted player controls.
Whenever enchanted player becomes the target of a spell you control, you gain 1 life.

When Scanning Module enters, crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)
Equipped creature gets +1/+1.
Equip {1}

Advance {1}{B} (Cast this for {1}{B} to advance it as it enters. {1}{B}: Advance this as a sorcery.)
Whenever Scarcrawler advances, you lose life equal to its power, then put a +1/+1 counter on it.

Whenever Scarhide, Arsenal Crafter attacks, create a token that's a copy of an Equipment attached to Scarhide and attach the token to Scarhide. When you can't, arm it. (Create a colorless Equipment artifact token with “Equipped creature gets +1/+0” and equip {2}, then attach it to that creature.)

Prowess, haste
You may spend mana as though it were mana of any color to cast noncreature spells with mana value 3 or less.

At the beginning of your end step, each opponent loses 1 life for each permanent they own that you control.

Whenever Scavenger of the Old Bay deals combat damage to a player, draw a card.
Ride {1}{U} ({1}{U}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Exile target creature with mana value 2 or less.

As an additional cost to cast Scavenger's Skill, you may reappropriate. (To reappropriate, exile exactly two cards from your hand and/or graveyard.)
Scavenger's Skill deals 3 damage to target creature or planeswalker. When that permanent dies this turn, if Scavenger's Skill's additional cost was paid, draw a card.

Scavenging Soldier has first strike as long as it's attacking.
Attain {3}{W} ({3}{W}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

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.