Demystify

Prosperous Pirates

When Prosperous Pirates enters, create two Treasure tokens. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Unknown Shores

{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Gilded Sentinel

Deeproot Champion

Whenever you cast a noncreature spell, put a +1/+1 counter on Deeproot Champion.

Spike-Tailed Ceratops

Spike-Tailed Ceratops can block an additional creature each combat.

Merfolk Branchwalker

When Merfolk Branchwalker enters, it explores. (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.)

Jungle Delver

{3}{G}: Put a +1/+1 counter on Jungle Delver.

Thrash of Raptors

As long as you control another Dinosaur, Thrash of Raptors gets +2/+0 and has trample.

Blossom Dryad

Storm Sculptor

Storm Sculptor can't be blocked.
When Storm Sculptor enters, return a creature you control to its owner's hand.

Conqueror's Foothold

(Transforms from Conqueror's Galleon.)
{T}: Add {C}.
{2}, {T}: Draw a card, then discard a card.
{4}, {T}: Draw a card.
{6}, {T}: Return target card from your graveyard to your hand.

Conqueror's Galleon

When Conqueror's Galleon attacks, exile it at end of combat, then return it to the battlefield transformed under your control.
Crew 4 (Tap any number of creatures you control with total power 4 or more: This Vehicle becomes an artifact creature until end of turn.)

Conqueror's Galleon // Conqueror's Foothold

Prying Blade

Equipped creature gets +1/+0.
Whenever equipped creature deals combat damage to a player, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Pirate's Prize

Draw two cards. Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Shapers of Nature

{3}{G}: Put a +1/+1 counter on target creature.
{2}{U}, Remove a +1/+1 counter from a creature you control: Draw a card.

Unclaimed Territory

As Unclaimed Territory enters, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type.

Watertrap Weaver

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

Headwater Sentries

Depths of Desire

Return target creature to its owner's hand. Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Daring Saboteur

{2}{U}: Daring Saboteur can't be blocked this turn.
Whenever Daring Saboteur deals combat damage to a player, you may draw a card. If you do, discard a card.

Run Aground

Put target artifact or creature on top of its owner's library.

Sky Terror

Shaper Apprentice

Shaper Apprentice has flying as long as you control another Merfolk.

Anointed Deacon

At the beginning of combat on your turn, you may have target Vampire get +2/+0 until end of turn.

Forest

Wind Strider

Flash (You may cast this spell any time you could cast an instant.)
Flying

Kopala, Warden of Waves

Spells your opponents cast that target a Merfolk you control cost {2} more to cast.
Abilities your opponents activate that target a Merfolk you control cost {2} more to activate.

Kumena's Speaker

Kumena's Speaker gets +1/+1 as long as you control another Merfolk or an Island.

Dire Fleet Hoarder

When Dire Fleet Hoarder dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Tishana's Wayfinder

When Tishana's Wayfinder enters, it explores. (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.)

Navigator's Ruin

Raid — At the beginning of your end step, if you attacked this turn, target opponent mills four cards.

Snapping Sailback

Flash
Enrage — Whenever Snapping Sailback is dealt damage, put a +1/+1 counter on it. (It must survive the damage to get the counter.)

Revel in Riches

Whenever a creature an opponent controls dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
At the beginning of your upkeep, if you control ten or more Treasures, you win the game.

Ixalli's Keeper

{7}{G}, {T}, Sacrifice Ixalli's Keeper: Target creature gets +5/+5 and gains trample until end of turn.

Pterodon Knight

Pterodon Knight has flying as long as you control a Dinosaur.

Island

Deeproot Warrior

Whenever Deeproot Warrior becomes blocked, it gets +1/+1 until end of turn.

River Sneak

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