msem-instigator

Scion of Belmord has lifelink as long as it's embattled. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Disgraced 1 (This enters with a -1/-1 counter. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)
Whenever you put one or more -1/-1 counters on Scion of Fiends or another creature, Scion of Fiends deals that much damage to each opponent.

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

Flying
Civilized — Scion of Sannuria has vigilance as long as you control an artifact, a creature, and an enchantment.

When Scion of Sarrithaz enters, create a 2/2 black Zombie creature token.
{2}{B}, Sacrifice a creature: Draw a card.

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.

Scion of the Wild's power and toughness are each equal to the number of creatures you control.

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

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.

Draw two cards.
Flashback—{2}{U}, Discard a card. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Scorch deals 3 damage to any target.

Enchant creature
Enchanted creature gets +2/-2.

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.

Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever a creature with wither deals combat damage to an opponent, Scorchmark Seer deals 2 damage to that player.

Flying
When Scorchpass Sovereign enters, it deals 1 damage to each creature with flying you don't control.

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

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.

When Scorpid Sniper enters, you may have target creature get -1/-1 until end of turn.

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

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

(Add a quest counter as this enters. Sacrifice after 3.)
Whenever you cast a noncreature spell, add a quest counter.
1, 2 — Draw a card, then discard a card.
3 — Return up to two target instant and/or sorcery cards from your graveyard to your hand.
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Scoured Barrens enters tapped.
When Scoured Barrens enters, you gain 1 life.
{T}: Add {W} or {B}.

Scoured Mesa enters tapped.
{T}: Add {W}.
Desertcycling {1}{W} ({1}{W}, Discard this card: Search your library for a Desert card, reveal it, and put it into your hand, then shuffle.)