msem-instigator

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

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
When Scion of Storms enters, create a 2/2 white Elemental creature token with flying.
Whenever a Plains you control enters, you may aetherize Scion of Storms. (To aetherize, create a token that's a copy of it, then exile that token.)

Flying
When Scion of Torrents enters, you may return target nonland permanent to its owner's hand.
Whenever an Island you control enters, you may aetherize Scion of Torrents. (To aetherize, create a token that's a copy of it, then exile that token.)

First strike
Whenever Scion of the Pack enters or one or more creatures you control deal combat damage to an opponent or planeswalker, create a 2/2 green Hound creature token.

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.

As Scorched Copse enters, you may tap an untapped creature you control. If you don't, Scorched Copse enters tapped.
{T}: Add {R} or {G}.

Enchant creature
Enchanted creature gets +2/-2.

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.

Flash
When Scorned Arcanist enters, until end of turn if a creature would enter the battlefield, instead exile that creature and that creature's controller amasses Soldiers X, where X is that creature's mana value. (They put X +1/+1 counters on an Army they control. It's also a Soldier. If they don't control an Army, they create a 0/0 black Soldier Army creature token first.)

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

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.
Draw a card, then discard a card.
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.)

Engorge (As this enters, mill three cards, then exile a card from among the milled cards.)
When Scourge of the Deadlands enters, if it engorged a creature card, each other player sacrifices a creature.

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.)