msem-instigator

Sludge-Gill Fox can't be blocked as long as it's attacking alone.
Whenever Sludge-Gill Fox deals combat damage to a player, you may draw a card.

{2}, Remove a +1/+1 counter from a creature you control: Draw a card.

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
{2}{B}, Sacrifice Sluiceway Shrieker: Put the bottom card of your library into your hand.

Whenever Slyten Connoisseur attacks, crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)
Once each turn, when an artifact you control dies, you may pay 1 life. If you do, draw a card.

Flying
{R}: Slyten Ignitor gets +1/+0 until end of turn.

Whenever Slyten Jewel Runner attacks, target creature can't block until end of turn.
Augmented — At the beginning of your end step, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on Slyten Jewel Runner.

When Smashing Brute enters, target nonbasic permanent loses all abilities until your next turn.
Foresight — Whenever you draw your second card each turn, you may exile Smashing Brute. If you do, return it to the battlefield.

When Smirk enters, add the top two cards of your library to your evil plan. (Look at them, then exile them face-down. You may pay {7} once a turn as a sorcery to cast any number of cards in your evil plan without paying their mana costs.)
Whenever you cast your second spell each turn, you draw a card and you lose 2 life.

When Smuggler of the Santriza enters, you may discard a card. If you do, draw a card.

Sneaking Capuchin can't be blocked except by creatures with defender.
{U}: Counter target spell or ability that targets Sneaking Capuchin.

Prowess
When Snowline Ascetic enters, you may put target instant or sorcery card from your graveyard on top of your library.

Flying
When Soaring Skymage enters, mill four cards. You may return a creature card with flying from among the milled cards to your hand.

Whenever you cast a noncreature spell, this creature gets +1/+0 and gains first strike until end of turn. Surveil 1.

Whenever Soli Arbalist or a nontoken Angel or Nephilim you control enters, amass Soldiers 2. If it was an Angel, amass Soldiers 4 instead. (To amass Soldiers {2}, put two +1/+1 counters on an Army you control. It's also a Soldier. If you don't control one, create a 0/0 black Soldier Army creature token first.)

When Soli Chronicler enters, judge another target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

Flying
Whenever Soli Windreader attacks, tap target creature without flying you don't control.

At the beginning of each player's upkeep, that player may pay {2} or 2 life. If they don't, they return a permanent they control to its owner's hand.

Whenever another creature you control enters, target opponent loses 1 life and you gain 1 life.
Sacrifice Somber River Bearer: Creatures you control gain indestructible until end of turn.

You may look at the top card of your library any time.
You may play lands from your graveyard and the top of your library.

Somberwald Rider can't be blocked by creatures with power 2 or less.
{2}{G}: Transform Somberwald Rider. Activate only if it's attacking.

Soul of Misery gets +1/+1 as long as you control a Swamp.
{4}{B}: Target player discards a card. Activate only as a sorcery.

Other Spirits you control get +1/+1.
As long as a Spirit you control has flying, Soulcleaver has flying. The same is true for first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance.

At the beginning of each end step, if you gained life this turn, put a +1/+1 counter on a creature you control.

Flash
Other Rogues you control get +1/+1.
Rogue spells you cast have flash.

Soulsmoke Adept gets +1/+0 and has lifelink as long as it's embattled. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)