Champions of the Shoal

As an additional cost to cast this spell, behold a Merfolk and exile it. (Exile a Merfolk you control or a Merfolk card from your hand.)
Whenever this creature enters or becomes tapped, tap up to one target creature and put a stun counter on it.
When this creature leaves the battlefield, return the exiled card to its owner's hand.

Ride's End

This spell costs {3} less to cast if it targets a tapped permanent.
Exile target creature or Vehicle.

Rest in Peace

When this enchantment enters, exile all graveyards.
If a card or token would be put into a graveyard from anywhere, exile it instead.

Split Up

Choose one —
• Destroy all tapped creatures.
• Destroy all untapped creatures.

Tishana's Tidebinder

Flash
When this creature enters, counter up to one target activated or triggered ability. If an ability of an artifact, creature, or planeswalker is countered this way, that permanent loses all abilities for as long as this creature remains on the battlefield. (Mana abilities can't be targeted.)

Annul

Counter target artifact or enchantment spell.

Flashfreeze

Seam Rip

When this enchantment enters, exile target nonland permanent an opponent controls with mana value 2 or less until this enchantment leaves the battlefield.

Deepway Navigator

Flash
When this creature enters, untap each other Merfolk you control.
As long as you attacked with three or more Merfolk this turn, Merfolk you control get +1/+0.

Plains

Mindspring Merfolk

Exhaust — {X}{U}{U}, {T}: Draw X cards. Put a +1/+1 counter on each Merfolk creature you control. (Activate each exhaust ability only once.)

Pinnacle Starcage

When this artifact enters, exile all artifacts and creatures with mana value 2 or less until this artifact leaves the battlefield.
{6}{W}{W}: Put each card exiled with this artifact into its owner's graveyard, then create a 2/2 colorless Robot artifact creature token for each card put into a graveyard this way. Sacrifice this artifact.

Eclipsed Merrow

When this creature enters, look at the top four cards of your library. You may reveal a Merfolk, Plains, or Island card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Floodpits Drowner

Flash
Vigilance
When this creature enters, tap target creature an opponent controls and put a stun counter on it.
{1}{U}, {T}: Shuffle this creature and target creature with a stun counter on it into their owners' libraries.

Deepchannel Duelist

At the beginning of your end step, untap target Merfolk you control.
Other Merfolk you control get +1/+1.

Sygg's Command

Choose two —
• Create a token that's a copy of target Merfolk you control.
• Creatures target player controls gain lifelink until end of turn.
• Target player draws a card.
• Tap target creature. Put a stun counter on it.

Negate

Island

Sharae of Numbing Depths

When Sharae enters, tap target creature an opponent controls and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Whenever you tap one or more untapped creatures your opponents control, draw a card. This ability triggers only once each turn.

Eclipsed Realms

As this land enters, choose Elemental, Elf, Faerie, Giant, Goblin, Kithkin, Merfolk, or Treefolk.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a spell of the chosen type or activate an ability of a source of the chosen type.

No More Lies

Counter target spell unless its controller pays {3}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Wanderbrine Trapper

{1}, {T}, Tap another untapped creature you control: Tap target creature an opponent controls.

Hallowed Fountain

({T}: Add {W} or {U}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Soul-Guide Lantern

When this artifact enters, exile target card from a graveyard.
{T}, Sacrifice this artifact: Exile each opponent's graveyard.
{1}, {T}, Sacrifice this artifact: Draw a card.