Silvergill Adept

As an additional cost to cast this spell, reveal a Merfolk card from your hand or pay {3}.
When this creature enters, draw a card.

Woodland Stream

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

Island

Kumena, Tyrant of Orazca

Tap another untapped Merfolk you control: Kumena can't be blocked this turn.
Tap three untapped Merfolk you control: Draw a card.
Tap five untapped Merfolk you control: Put a +1/+1 counter on each Merfolk you control.

Forest

River Heralds' Boon

Put a +1/+1 counter on target creature and a +1/+1 counter on up to one target Merfolk.

Deeproot Champion

Whenever you cast a noncreature spell, put a +1/+1 counter on this creature.

Deeproot Elite

Whenever another Merfolk you control enters, put a +1/+1 counter on target Merfolk you control.

Hinterland Harbor

This land enters tapped unless you control a Forest or an Island.
{T}: Add {G} or {U}.

Watertrap Weaver

When this creature enters, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Kumena's Speaker

This creature gets +1/+1 as long as you control another Merfolk or an Island.

Sleep

Tap all creatures target player controls. Those creatures don't untap during that player's next untap step.

Jade Bearer

When this creature enters, put a +1/+1 counter on another target Merfolk you control.

River Sneak

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

Tempest Caller

When this creature enters, tap all creatures target opponent controls.

Merfolk Mistbinder

Seafloor Oracle

Whenever a Merfolk you control deals combat damage to a player, draw a card.

Disperse

Return target nonland permanent to its owner's hand.

Jungleborn Pioneer

When this creature enters, create a 1/1 blue Merfolk creature token with hexproof. (It can't be the target of spells or abilities your opponents control.)

Herald of Secret Streams

Creatures you control with +1/+1 counters on them can't be blocked.

Jadelight Ranger

When this creature enters, it explores, then it explores again. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard. Then repeat this process.)