Drowner of Secrets

Tap an untapped Merfolk you control: Target player mills a card.

River Merfolk

{U}: This creature gains mountainwalk until end of turn. (It can't be blocked as long as defending player controls a Mountain.)

Stonybrook Schoolmaster

Whenever this creature becomes tapped, you may create a 1/1 blue Merfolk Wizard creature token.

Plains

Serendib Sorcerer

{T}: Target creature other than this creature has base power and toughness 0/2 until end of turn.

Boreal Shelf

This land enters tapped.
{T}: Add {W} or {U}.

Harpoon Sniper

{W}, {T}: This creature deals X damage to target attacking or blocking creature, where X is the number of Merfolk you control.

Drifting Meadow

This land enters tapped.
{T}: Add {W}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Seasinger

When you control no Islands, sacrifice this creature.
You may choose not to untap this creature during your untap step.
{T}: Gain control of target creature whose controller controls an Island for as long as you control this creature and this creature remains tapped.

Surgespanner

Whenever this creature becomes tapped, you may pay {1}{U}. If you do, return target permanent to its owner's hand.

Soaring Hope

Enchant creature
When this Aura enters, you gain 3 life.
Enchanted creature has flying.
{W}: Put this Aura on top of its owner's library.

Manta Riders

{U}: This creature gains flying until end of turn.

Merfolk Raiders

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Phasing (This phases in or out before you untap during each of your untap steps. While it's phased out, it's treated as though it doesn't exist.)

Wellgabber Apothecary

{1}{W}: Prevent all damage that would be dealt to target tapped Merfolk or Kithkin creature this turn.

Cloudcrest Lake

{T}: Add {C}.
{T}: Add {W} or {U}. This land doesn't untap during your next untap step.

Merrow Levitator

{T}: Target creature gains flying until end of turn.
Whenever you cast a blue spell, you may untap this creature.

Aquitect's Will

Put a flood counter on target land. That land is an Island in addition to its other types for as long as it has a flood counter on it. If you control a Merfolk, draw a card.

Silvergill Douser

{T}: Target creature gets -X/-0 until end of turn, where X is the number of Merfolk and/or Faeries you control.

Stonybrook Banneret

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Merfolk spells and Wizard spells you cast cost {1} less to cast.

Vesuva

You may have this land enter tapped as a copy of any land on the battlefield.

Summon the School

Create two 1/1 blue Merfolk Wizard creature tokens.
Tap four untapped Merfolk you control: Return this card from your graveyard to your hand.

Hold the Line

Blocking creatures get +7/+7 until end of turn.

Triclopean Sight

Flash
Enchant creature
When this Aura enters, untap enchanted creature.
Enchanted creature gets +1/+1 and has vigilance.

Merfolk Thaumaturgist

{T}: Switch target creature's power and toughness until end of turn.

Veteran of the Depths

Whenever this creature becomes tapped, you may put a +1/+1 counter on it.

Remote Isle

This land enters tapped.
{T}: Add {U}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Neck Snap

Destroy target attacking or blocking creature.

Island

Benthicore

When this creature enters, create two 1/1 blue Merfolk Wizard creature tokens.
Tap two untapped Merfolk you control: Untap this creature. It gains shroud until end of turn. (It can't be the target of spells or abilities.)

Wanderwine Prophets

Champion a Merfolk (When this enters, sacrifice it unless you exile another Merfolk you control. When this leaves the battlefield, that card returns to the battlefield.)
Whenever this creature deals combat damage to a player, you may sacrifice a Merfolk. If you do, take an extra turn after this one.

Judge of Currents

Whenever a Merfolk you control becomes tapped, you may gain 1 life.

Merrow Commerce

At the beginning of your end step, untap all Merfolk you control.

Secluded Steppe

This land enters tapped.
{T}: Add {W}.
Cycling {W} ({W}, Discard this card: Draw a card.)

Clone

You may have this creature enter as a copy of any creature on the battlefield.

Psionic Blast

Psionic Blast deals 4 damage to any target and 2 damage to you.

Inkfathom Divers

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
When this creature enters, look at the top four cards of your library, then put them back in any order.

Streambed Aquitects

{T}: Target Merfolk creature gets +1/+1 and gains islandwalk until end of turn. (It can't be blocked as long as defending player controls an Island.)
{T}: Target land becomes an Island until end of turn.

Fallowsage

Whenever this creature becomes tapped, you may draw a card.

Merrow Reejerey

Other Merfolk creatures you control get +1/+1.
Whenever you cast a Merfolk spell, you may tap or untap target permanent.

Amoeboid Changeling

Changeling (This card is every creature type.)
{T}: Target creature gains all creature types until end of turn.
{T}: Target creature loses all creature types until end of turn.