Riptide Biologist

Creature — Human Wizard (1/2)

Protection from Beasts
Morph (You may cast this card face down as a 2/2 creature for . Turn it face up any time for its morph cost.)

Riptide Mangler

Creature — Beast (0/3)

: Change Riptide Mangler's base power to target creature's power. (This effect lasts indefinitely.)

Riptide Turtle

Creature — Turtle (0/5)

Flash
Defender

River Sneak

Creature — Merfolk Warrior (1/1)

River Sneak can't be blocked.
Whenever another Merfolk enters the battlefield under your control, River Sneak gets +1/+1 until end of turn.

Roil Cartographer

Creature — Merfolk Rogue (1/3)

Landfall — Whenever a land enters the battlefield under your control, you get (an energy counter).
, Pay six : Draw three cards.

Sage of Lat-Nam

Creature — Human Artificer (1/2)

, Sacrifice an artifact: Draw a card.

Sage of the Unknowable

Creature — Human Wizard (0/4)

: Add . Spend this mana only to cast a colorless spell or to activate an ability.

Sage's Row Savant

Creature — Vedalken Wizard (2/1)

When Sage's Row Savant enters the battlefield, scry 2.

Saiba Cryptomancer

Creature — Moonfolk Ninja (0/1)

Flash
Backup 1 (When this creature enters the battlefield, put a +1/+1 counter on target creature. If that's another creature, it gains the following ability until end of turn.)
Hexproof

Sapphire Leech

Creature — Leech (2/2)

Flying
Blue spells you cast cost more to cast.

Saprazzan Heir

Creature — Merfolk (1/1)

Whenever Saprazzan Heir becomes blocked, you may draw three cards.

School of Piranha

Creature — Fish (3/3)

At the beginning of your upkeep, sacrifice School of Piranha unless you pay .

Screeching Skaab

Creature — Zombie (2/1)

When Screeching Skaab enters the battlefield, mill two cards.

Sea Eagle

Creature — Bird (1/1)

Flying

Sea Gate Stormcaller

Creature — Human Wizard (2/1)

Kicker
When Sea Gate Stormcaller enters the battlefield, copy the next instant or sorcery spell with mana value 2 or less you cast this turn when you cast it. If Sea Gate Stormcaller was kicked, copy that spell twice instead. You may choose new targets for the copies.

Sea Scryer

Creature — Merfolk Wizard (1/1)

: Add .
, : Add .

Sea Sprite

Creature — Faerie (1/1)

Flying, protection from red

Seacoast Drake

Creature — Drake (1/3)

Flying

Seagraf Skaab

Creature — Zombie (1/3)

Sejiri Merfolk

Creature — Merfolk Soldier (2/1)

As long as you control a Plains, Sejiri Merfolk has first strike and lifelink. (Damage dealt by a creature with lifelink also causes its controller to gain that much life.)