msem-instigator

Deathtouch
Inspired — Whenever Scar Tattooist becomes untapped, you may have target creature get -1/-1 until end of turn.

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

Crew 1 (Tap any number of creatures you control with total power 1 or greater: This Vehicle becomes an artifact creature until end of turn.)
Whenever Scavengermobile deals combat damage to a player, choose land or nonland, then rediscover a card of that kind. (Look at the top card of your library. You may reveal it and put it into your hand if it's a card of the chosen type. Otherwise, put it back or into your graveyard.)

Whenever another creature dies, you gain 1 life.

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.)

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.”)

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

When Scion of Fecundity enters, search your library for a creature card with mana value 2 or less, reveal that card, put it into your hand, then shuffle.
Revive—{1}{G}{W}, Discard a card. ({1}{G}{W}, Discard a card, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

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.

As Scion of Silence enters, choose a nonland card name.
Other permanents with the chosen name lose all abilities.

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.

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

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.

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
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.

Scrap, the Second Myr has all activated abilities of other artifact creatures you control.

When Scrapgear Contraption dies, you may put a +1/+1 counter on target creature.

Vigilance, trample

{3}{B}, Exile Screeching Duneborn from your graveyard: You gain 1 life and draw a card.