msem-instigator

Whenever an opponent is dealt damage by one or more sources you control for the second time each turn, draw a card.

Whenever Skitterthorns blocks or becomes blocked, creatures you control gain deathtouch until end of turn.

Create a 1/1 green Squirrel creature token.
The next creature spell you cast this turn can be cast as though it had flash. As you cast that spell, it gains voracious 2. (As it enters, you may sacrifice up to two artifacts and/or creatures. That creature enters with that many +1/+1 counters on it.)

Until end of turn, target creature you control gets +1/+1 and target creature an opponent controls gets -1/-1.

{3}{W}: Tap target creature with power 4 or greater.

Trample, haste
Skullbriar gets +1/+1 for each creature card in all graveyards.
{T}: Add {B} or {G}.
Skullbriar, Death's Mockery remains transformed as it moves to any zone other than a player's hand or library.

Sky-High Spires enters tapped unless you have two or more opponents.
{T}: Add {W} or {U}.

Enchant creature
Enchanted creature gets +1/+1 and has flying.

Return up to one target creature to its owner's hand. Then if this spell was foretold, you may destroy all creatures.
Foretell {1}{W}{W}{U} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Skylight Fortress enters tapped.
When Skylight Fortress enters, you may search your library for a card named Skylight Fortress, reveal it, put it into your hand, then shuffle.
{T}: Add {C}.

At the beginning of combat on your turn, target creature you control with flying gets +1/+1 until end of turn.

Target creature blocks this turn if able. You may have it gain reach until end of turn.
Draw a card.

Look at the top two cards of your library. Put one of them into your hand and the other on the bottom of your library.

Equipped creature has “{1}, {T}: This creature deals 1 damage to any target.”
Whenever equipped creature deals damage to a creature with power 5 or greater, sacrifice Sling of the Meek. If you do, destroy that creature.
Equip {3}

Slinking Raider can't be blocked by creatures with greater power.
Whenever Slinking Raider deals damage to a player or noncreature permanent, put a +1/+1 counter on it.
Surpass {5}{R} ({5}{R}: Transform this creature.
This costs {1} less to activate for each counter on it. Activate only as a sorcery.)

Slipsand Oasis enters tapped unless you played it from exile.
{T}: Add {W} or {B}.

Slipstream Horizon enters tapped.
{T}: Add {U} or {R}.
{U}{R}, {T}, Sacrifice Slipstream Horizon: Conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)

(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.

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

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

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

You draw a card and you lose 1 life. Exile Small Luxuries.
At the beginning of your upkeep, you may return Small Luxuries from your graveyard to your hand.

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.