msem-instigator

First strike
Disgraced 1 (This enters with a -1/-1 counter. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)

Scathing Review deals 2 damage to target creature. If you control an artifact, Scathing Review deals 2 damage to that creature's controller.

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.

Flying
Whenever Scavenging Hilakites attacks, you may sacrifice another creature. When you do, Scavenging Hilakites deals damage equal to the sacrificed creature's power to any target.

Choose one or both —
• Scene to Cinders deals 2 damage to each token creature.
• Scene to Cinders deals 2 damage to each nontoken creature.

Scholar of the Staff can't block.
Inspired — Whenever Scholar of the Staff becomes untapped, up to one target creature can't block this turn.

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

Whenever one or more nontoken Merfolk you control attack, create a 2/1 red Merfolk creature token.

Add three mana of any one color.

Menace
When Scion of Calamities enters, exile the top two cards of your library. Until the end of your next turn, you may play one of those cards.
Whenever a Mountain you control enters, you may aetherize Scion of Calamities. (To aetherize, create a token that's a copy of it, then exile that token.)

This spell costs {2} less to cast if its target has the same name as a card in a graveyard.
Scoff deals 3 damage to any target.

Scorch deals 3 damage to any target.

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.

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

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Scorchland Vandal attacks each combat if able.

Whenever you cast a spell, Scorned Figurant gets +1/+1 until end of turn.

Scornful Flames deals 4 damage to target player.
Dominance — Scornful Flames deals 1 damage to each creature that player controls if you control the creature with the greatest power or tied for the greatest power.

Scoundreleo enters with a +1/+1 counter on it if a creature you controlled dealt combat damage to a player this turn.

Double strike
Creatures you control have trample.
Excess noncombat damage that would be dealt by sources you control to permanents an opponent controls is dealt to that player instead.

Flying, haste
Ride {1}{R} ({1}{R}: Transform this and attach it to target creature you control without a Mount. Ride only as a sorcery.)

Flying, haste
Whenever Scourge of the Skies attacks, you may have it deal 5 damage to target creature.

Flying
Whenever you cast an instant or sorcery spell, Scourge of the Sun gets +1/+0 until end of turn. If you spent four or more mana to cast that spell, Scourge of the Sun gets an additional +1/+0 until end of turn.

Breach (Whenever this deals combat damage to a player, you may have it become an Aura Curse until your next turn. Attach it to that player.)
At the beginning of your end step, discard a card. Then draw a card if an opponent is cursed.

Sacrifice Scrapyard Raiders: Target artifact gains indestructible until end of turn.

Trample, prowess