Slither Blade

Dissolve

Counter target spell. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Expendable Lackey

{1}{U}, Exile this card from your graveyard: Create a 1/1 blue Fish creature token with "This token can't be blocked." Activate only as a sorcery.

Counterspell

Invisible Stalker

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
This creature can't be blocked.

Mist-Cloaked Herald

Triton Shorestalker

Island

River Sneak

This creature can't be blocked.
Whenever another Merfolk you control enters, this creature gets +1/+1 until end of turn.

Flitterstep Eidolon

Bestow {5}{U} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
This creature can't be blocked.
Enchanted creature gets +1/+1 and can't be blocked.

Gudul Lurker

This creature can't be blocked.
Megamorph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)

Ertai's Scorn

This spell costs {U} less to cast if an opponent cast two or more spells this turn.
Counter target spell.

Admiral's Order

Raid — If you attacked this turn, you may pay {U} rather than pay this spell's mana cost.
Counter target spell.

Aether Figment

Kicker {3} (You may pay an additional {3} as you cast this spell.)
If this creature was kicked, it enters with two +1/+1 counters on it.
This creature can't be blocked.