Underground River

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

Angler Turtle

Hexproof
Creatures your opponents control attack each combat if able.

Sinister Starfish

{T}: Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Leechridden Swamp

({T}: Add {B}.)
Leechridden Swamp enters the battlefield tapped.
{B}, {T}: Each opponent loses 1 life. Activate only if you control two or more black permanents.

Squelching Leeches

Squelching Leeches's power and toughness are each equal to the number of Swamps you control.

Marang River Prowler

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.

River Hoopoe

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

River Serpent

River Serpent can't attack unless there are five or more cards in your graveyard.
Cycling {U} ({U}, Discard this card: Draw a card.)

Putrid Leech

Pay 2 life: Putrid Leech gets +2/+2 until end of turn. Activate only once each turn.

Swamp

Mindleech Mass

Trample
Whenever Mindleech Mass deals combat damage to a player, you may look at that player's hand. If you do, you may cast a spell from among those cards without paying its mana cost.

River Sneak

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

Spiny Starfish

{U}: Regenerate Spiny Starfish.
At the beginning of each end step, if Spiny Starfish regenerated this turn, create a 0/1 blue Starfish creature token for each time it regenerated this turn.

Marang River Skeleton

{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.)

Island

Crocodile of the Crossing

Haste
When Crocodile of the Crossing enters the battlefield, put a -1/-1 counter on target creature you control.

River Darter

River Darter can't be blocked by Dinosaurs.

Blitz Leech

Flash
When Blitz Leech enters the battlefield, target creature an opponent controls gets -2/-2 until end of turn. Remove all counters from that creature.

River's Rebuke

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

Sigiled Starfish

{T}: Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Gurmag Angler

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)

Lurking Crocodile

Bloodthirst 1 (If an opponent was dealt damage this turn, this creature enters the battlefield with a +1/+1 counter on it.)
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

River of Tears

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

Blessing of Leeches

Flash
Enchant creature
At the beginning of your upkeep, you lose 1 life.
{0}: Regenerate enchanted creature.

Rushing River

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.

Waterlogged Grove

{T}, Pay 1 life: Add {G} or {U}.
{1}, {T}, Sacrifice Waterlogged Grove: Draw a card.

Mistford River Turtle

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

Archelos, Lagoon Mystic

As long as Archelos, Lagoon Mystic is tapped, other permanents enter the battlefield tapped.
As long as Archelos is untapped, other permanents enter the battlefield untapped.

Waterknot

Enchant creature
When Waterknot enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Forest

River's Grasp

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.)

You Come to a River

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.

Rootwater Mystic

{1}{U}: Look at the top card of target player's library.

Quagmire Lamprey

Whenever Quagmire Lamprey becomes blocked by a creature, put a -1/-1 counter on that creature.

Bad River

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.

Leech Bonder

Leech Bonder enters the battlefield with two -1/-1 counters on it.
{U}, {Q}: Move a counter from target creature onto a second target creature. ({Q} is the untap symbol.)

Cold-Water Snapper

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

Piranha Marsh

Piranha Marsh enters the battlefield tapped.
When Piranha Marsh enters the battlefield, target player loses 1 life.
{T}: Add {B}.

Rootwater Matriarch

{T}: Gain control of target creature for as long as that creature is enchanted.

Woodland Stream

Woodland Stream enters the battlefield tapped.
{T}: Add {G} or {U}.

River Boa

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
{G}: Regenerate River Boa.

Sygg, River Cutthroat

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.)

Moat Piranhas

River Bear

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

Rootwater Hunter

{T}: Rootwater Hunter deals 1 damage to any target.

Stinging Lionfish

Whenever you cast your first spell during each opponent's turn, you may tap or untap target nonland permanent.

Wandering Stream

Domain — You gain 2 life for each basic land type among lands you control.

River Kelpie

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.)