Riftwing Cloudskate

Flying
When this creature enters, return target permanent to its owner's hand.
Suspend 3—{1}{U} (Rather than cast this card from your hand, you may pay {1}{U} and exile it with three time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Sage of Epityr

When this creature enters, look at the top four cards of your library, then put them back in any order.

Screeching Sliver

All Slivers have "{T}: Target player mills a card."

Shadow Sliver

All Sliver creatures have shadow. (They can block or be blocked by only creatures with shadow.)

Morph

Slipstream Serpent

This creature can't attack unless defending player controls an Island.
When you control no Islands, sacrifice this creature.
Morph {5}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Snapback

You may exile a blue card from your hand rather than pay this spell's mana cost.
Return target creature to its owner's hand.

Spell Burst

Buyback {3} (You may pay an additional {3} as you cast this spell. If you do, put this card into your hand as it resolves.)
Counter target spell with mana value X.

Children of Korlis

Sacrifice this creature: You gain life equal to the life you've lost this turn. (Damage causes loss of life.)

Spiketail Drakeling

Flying
Sacrifice this creature: Counter target spell unless its controller pays {2}.

Sprite Noble

Flying
Other creatures you control with flying get +0/+1.
{T}: Other creatures you control with flying get +1/+0 until end of turn.

Stormcloud Djinn

Flying
This creature can block only creatures with flying.
{R}{R}: This creature gets +2/+0 until end of turn and deals 1 damage to you.

Teferi, Mage of Zhalfir

Flash
Creature cards you own that aren't on the battlefield have flash.
Each opponent can cast spells only any time they could cast a sorcery.

Telekinetic Sliver

All Slivers have "{T}: Tap target permanent."

Temporal Eddy

Put target creature or land on top of its owner's library.

Shellfish Scholar

Think Twice

Draw a card.
Flashback {2}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Tolarian Sentinel

Flying
{U}, {T}, Discard a card: Return target permanent you control to its owner's hand.

Time Spiral