msem-instigator

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.

Prowess
When Scarlands Singularity enters, each player conjures a card named Data-Point into their hand. (It's a sorcery that costs {2} with “Draw a card.”)

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

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.)

Whenever Scathing Critics deals combat damage to a player or planeswalker, put a +1/+1 counter on it.

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.)

Whenever another creature dies, you gain 1 life.

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.

Reach
When Scavenging Pack enters, you may destroy target artifact with mana value 2 or less.

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.”)

Flying
{1}{U}, Sacrifice Scholar's Assistant: Draw a card.

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.)

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.)

Deathtouch
When Scion of Desolation enters, put target creature card with mana value 3 or less from a graveyard onto the battlefield under your control.
Whenever a Swamp you control enters, you may aetherize Scion of Desolation. (To aetherize, create a token that's a copy of it, then exile that token.)

Trample
When Scion of Flourishing enters, put a +1/+1 counter on each other creature you control. Those creatures gain trample until end of turn.
Whenever a Forest you control enters, you may aetherize Scion of Flourishing. (To aetherize, create a token that's a copy of it, then exile that token.)

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

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.

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.)

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.

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

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

Menace
Sacrifice another artifact: Scrap Buggy becomes an artifact creature until end of turn.
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

When Scrivener of Sha'Iv enters, draw a card and adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)

At the beginning of your upkeep, if six or more cards are in your graveyard, you may transform Scuttling Gnat.