msem-instigator

{1}, {T}: Surveil 2.
{U}, {T}, Discard a card: Look at the top card of your library. If it's a nonland card, you may cast it. (You still pay its costs)

As long as there are four or more card types among cards in your graveyard, Slipstream Silencer can't be blocked.
Whenever Slipstream Silencer attacks, surveil 1.

Whenever Slithering Eyes deals damage to a player, you may exile that many cards from the top of your library. Until the end of your next turn, you may play those cards.

(Transform this if it's not attached to a creature. Pay {2}{W} as a sorcery to unattach it.)
Enchant creature you control
Slopestrider's Chariot's rider gets +1/+1 and has double strike.

Vanguard — Whenever a creature you control attacks alone, you may exile target instant or sorcery card from your graveyard. If you do, you may cast that spell from exile until your next turn. If that spell would be put into a graveyard, exile it instead.

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.

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.

Deathtouch
When Slum Scrounger enters, put up to two target creature cards in your graveyard on top of your library in any order.

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Slums Thug gets +1/+1 and has menace as long as you've gained life this turn.

First strike
{2}{R}: Monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous.)

When Slyten Analyst enters, you may search your library for a card, then shuffle and put that card on top. If you do, you lose 2 life.

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.

{T}: Add {C}.
{4}, {T}, Sacrifice Slyten Crystal Motherlode: Add {W}{U}{B}{R}{G}.

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.

Whenever you cast a noncreature spell, Slyten Technician gets +1/+0 until end of turn, then scry 1.

Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.
Augmented — If you've spent {W}{U}{B}{R}{G} to cast spells this turn, put two of those cards into your hand instead.

Destroy target enchantment. If it's a Curse, you gain 3 life.

Choose target creature you don't control. When that creature dies this turn, draw a card. Target creature you control fights that creature.

Target creature gets +3/+3 until end of turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

Smelting Breath deals 5 damage to target creature. Destroy up to one Equipment attached to that creature.

Destroy target creature with power 4 or greater.

Goad up to one target creature. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)
Draw a card.

Target creature can't block this turn. Smokescreen deals 2 damage to that creature's controller.

When Smokeweaver Initiate dies, draw a card.