msem-instigator

Target creature gets -2/-2 until end of turn. Scry 1.

Death knell — You gain 2 life. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)

Draw a card, then forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

Haste
Sixpod Sprinter can't be blocked except by creatures with flying or reach.

When Skelephant enters, you may mill three cards.
Foresight — Whenever you draw your second card each turn, you may put target creature card from your graveyard on top of your library.

{T}, Sacrifice Skeletal Oasis: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

When Skeletal Shredwing enters, target creature can't block this turn.
Revive {5}{R} ({5}{R}, 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
Whenever Skhorvall Patrol deals combat damage to a player, look at the top card of that player's library.

When Skhorvall Raider enters, if you control an embattled creature, Skhorvall Raider deals 2 damage to any target. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Sacrifice another creature: Put a +1/+1 counter on Skieryg Menace.

Skin from Bone deals damage to target creature equal to your fealty to Mountains. (Each Mountain you control counts towards your fealty to Mountains.)

When Skittering Atrocity enters, up to one target creature gets -X/-X until end of turn, where X is the number of Horrors you control.

Reach

Advance {3}{R}{R} (Cast this for {3}{R}{R} to advance it as it enters. {3}{R}{R}: Advance this as a sorcery.)
Flying, haste
Whenever Skiviar Scraplord advances, put a +1/+1 counter on it.

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

Flying
Death knell — Skullhoarder Dragon gets +2/+0 until end of turn. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)

Flying
When Sky-Torrent Navigator enters, forebode. If you control two or more Pirates, forebode again. (To forebode, create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

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

Flying
Cycling {U} ({U}, Discard this card: Draw a card.)

Flying
Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)

Flying
Whenever Skyline Climber attacks, another target creature you control gains flying until end of turn.

Flying
When Skymount Reinforcements enters, put a +1/+1 counter on another target creature.

{1}{U}: Skysail Rigger voyages. (If it isn't blocking or targeted by another spell or ability, it phases out.)
Whenever Skysail Rigger phases in, put a flying counter on it.

Skysworn Aspirant has flying 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.)

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