Bad River enters the battlefield tapped.

{T}, Sacrifice Bad River: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

{T}: Add {U}.

{T}: Add {B}.

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Whenever Cold-Eyed Selkie deals combat damage to a player, you may draw that many cards.

Dauntless River Marshal gets +1/+1 as long as you control an Island.

{3}{U}: Tap target creature.

Blue creatures you control can't be blocked.

Return up to two target creatures to their owners' hands.

Cycling {2} ({2}, Discard this card: Draw a card.)

Hinterland Harbor enters the battlefield tapped unless you control a Forest or an Island.

{T}: Add {G} or {U}.

Marang River Prowler can't block and can't be blocked.

You may cast Marang River Prowler from your graveyard as long as you control a black or green permanent.

{B}: Regenerate Marang River Skeleton.

Megamorph {3}{B} (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.)

Meandering River enters the battlefield tapped.

{T}: Add {W} or {U}.

Whenever Mistford River Turtle attacks, another target attacking non-Human creature can't be blocked this turn.

Whenever one or more creatures you control attack, each defending player divides all creatures without flying they control into a "left" pile and a "right" pile. Then, for each attacking creature you control, choose "left" or "right." That creature can't be blocked this combat except by creatures with flying and creatures in a pile with the chosen label.

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

{G}: Regenerate River Boa.

River Darter can't be blocked by Dinosaurs.

River Delta doesn't untap during your untap step if it has a depletion counter on it.

At the beginning of your upkeep, remove a depletion counter from River Delta.

{T}: Add {U} or {B}. Put a depletion counter on River Delta.

Vigilance

When River Herald Guide enters the battlefield, 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.)

When River Herald Scout enters the battlefield, 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.)

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

Flying

{3}{G}{U}: You gain 2 life and draw a card.

Whenever River Kelpie or another permanent enters the battlefield from a graveyard, draw a card.

Whenever a player casts a spell from a graveyard, draw a card.

Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

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

River Serpent can't attack unless there are five or more cards in your graveyard.

Cycling {U} ({U}, Discard this card: Draw a card.)

River Sneak can't be blocked.

Whenever another Merfolk enters the battlefield under your control, River Sneak gets +1/+1 until end of turn.

{T}: Add {U}. If you played a land this turn, add {B} instead.

Enchant creature

Enchanted creature gets +1/+1.

If {U} was spent to cast this spell, return up to one target creature to its owner's hand. If {B} was spent to cast this spell, target player reveals their hand, you choose a nonland card from it, then that player discards that card. (Do both if {U}{B} was spent.)

Return all nonland permanents target player controls to their owner's hand.

{T}: Add {U}.

{T}: Add {R}.

Flying

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

When Riverwise Augur enters the battlefield, draw three cards, then put two cards from your hand on top of your library in any order.

Kicker--Sacrifice a land. (You may sacrifice a land in addition to any other costs as you cast this spell.)

Return target nonland permanent to its owner's hand. If this spell was kicked, return another target nonland permanent to its owner's hand.

Enchant land (Target a land as you cast this. This card enters the battlefield attached to that land.)

Enchanted land is an Island.

Flash

When Singer of Swift Rivers enters the battlefield, put a shield counter on another target creature you control. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

You may cast Merfolk spells as though they had flash.

Flying

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

Enchant land

When Spreading Seas enters the battlefield, draw a card.

Enchanted land is an Island.

{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.

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

Cycling {U} ({U}, Discard this card: Draw a card.)

At the beginning of each end step, if an opponent lost 3 or more life this turn, you may draw a card. (Damage causes loss of life.)

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

{1}{W}: Target Merfolk you control gains protection from the color of your choice until end of turn.

{T}: Add {C}.

{T}: Add {U} or {B}. Underground River deals 1 damage to you.

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

Return up to two target creatures to their owners' hands.

Constellation -- Whenever Whitewater Naiads or another enchantment enters the battlefield under your control, target creature can't be blocked this turn.

When Wistful Selkie enters the battlefield, draw a card.

Choose one --

• Fight the Current -- Return target nonland permanent to its owner's hand.

• Find a Crossing -- Target creature gets +1/+0 until end of turn and can't be blocked this turn.