Rootwater Commando

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

Blistergrub

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
When Blistergrub dies, each opponent loses 2 life.

Sewerdreg

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Sacrifice Sewerdreg: Exile target card from a graveyard.

Lingering Mirage

Enchant land
Enchanted land is an Island.
Cycling {2} ({2}, Discard this card: Draw a card.)

Dragonskull Summit

Dragonskull Summit enters tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

Bog Raiders

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)

Plague Beetle

Mutilate

All creatures get -1/-1 until end of turn for each Swamp you control.

Shimmering Mirage

Target land becomes the basic land type of your choice until end of turn.
Draw a card.

Chasm Skulker

Whenever you draw a card, put a +1/+1 counter on Chasm Skulker.
When Chasm Skulker dies, create X 1/1 blue Squid creature tokens with islandwalk, where X is the number of +1/+1 counters on Chasm Skulker. (They can't be blocked as long as defending player controls an Island.)

Filth

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
As long as Filth is in your graveyard and you control a Swamp, creatures you control have swampwalk.

Tainted Well

Enchant land
When Tainted Well enters, draw a card.
Enchanted land is a Swamp.

Mystic Compass

{1}, {T}: Target land becomes the basic land type of your choice until end of turn.

Crumbling Necropolis

Crumbling Necropolis enters tapped.
{T}: Add {U}, {B}, or {R}.

Thada Adel, Acquisitor

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Thada Adel, Acquisitor deals combat damage to a player, search that player's library for an artifact card and exile it. Then that player shuffles. Until end of turn, you may play that card.

Smoldering Marsh

({T}: Add {B} or {R}.)
Smoldering Marsh enters tapped unless you control two or more basic lands.

Terramorphic Expanse

{T}, Sacrifice Terramorphic Expanse: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Lashwrithe

Living weapon (When this Equipment enters, create a 0/0 black Phyrexian Germ creature token, then attach this to it.)
Equipped creature gets +1/+1 for each Swamp you control.
Equip {B/P}{B/P} ({B/P} can be paid with either {B} or 2 life.)

Blanket of Night

Each land is a Swamp in addition to its other land types.

Tolaria West

Tolaria West enters tapped.
{T}: Add {U}.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with mana value 0, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Whispering Shade

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
{B}: Whispering Shade gets +1/+1 until end of turn.

Defile

Target creature gets -1/-1 until end of turn for each Swamp you control.

Marsh Goblins

Maestros Theater

When Maestros Theater enters, sacrifice it. When you do, search your library for a basic Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle and you gain 1 life.

Bog Tatters

Sea's Claim

Enchant land (Target a land as you cast this. This card enters attached to that land.)
Enchanted land is an Island.

Viscid Lemures

{0}: Viscid Lemures gets -1/-0 and gains swampwalk until end of turn. (It can't be blocked as long as defending player controls a Swamp.)

Boggart Loggers

Forestwalk (This creature can't be blocked as long as defending player controls a Forest.)
{2}{B}, Sacrifice Boggart Loggers: Destroy target Treefolk or Forest.

Nightcreep

Until end of turn, all creatures become black and all lands become Swamps.

Street Wraith

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Cycling—Pay 2 life. (Pay 2 life, Discard this card: Draw a card.)

Contaminated Ground

Enchant land
Enchanted land is a Swamp.
Whenever enchanted land becomes tapped, its controller loses 2 life.

Moor Fiend

Anurid Murkdiver

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Cateran Slaver

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
{5}, {T}: Search your library for a Mercenary permanent card with mana value 5 or less, put it onto the battlefield, then shuffle.

Sewer Shambler

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Scavenge {2}{B} ({2}{B}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

Tideshaper Mystic

{T}: Target land becomes the basic land type of your choice until end of turn. Activate only during your turn.

Sol'kanar the Swamp King

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Whenever a player casts a black spell, you gain 1 life.

Mire's Toll

Target player reveals a number of cards from their hand equal to the number of Swamps you control. You choose one of them. That player discards that card.

Yavimaya, Cradle of Growth

Each land is a Forest in addition to its other land types.

Mountain

Witch Engine

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
{T}: Add {B}{B}{B}{B}. Target opponent gains control of Witch Engine. (Activate only as an instant.)

Quicksilver Fountain

At the beginning of each player's upkeep, that player puts a flood counter on target non-Island land they control of their choice. That land is an Island for as long as it has a flood counter on it.
At the beginning of each end step, if all lands on the battlefield are Islands, remove all flood counters from them.

Sol Ring

Slithery Stalker

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
When Slithery Stalker enters, exile target green or white creature an opponent controls.
When Slithery Stalker leaves the battlefield, return the exiled card to the battlefield under its owner's control.

Merfolk Spy

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Merfolk Spy deals combat damage to a player, that player reveals a card at random from their hand.

Koth's Courier

Forestwalk (This creature can't be blocked as long as defending player controls a Forest.)

Aquitect's Will

Put a flood counter on target land. That land is an Island in addition to its other types for as long as it has a flood counter on it. If you control a Merfolk, draw a card.

Slinking Serpent

Evil Presence

Dream Thrush

Flying
{T}: Target land becomes the basic land type of your choice until end of turn.

Reef Shaman

{T}: Target land becomes the basic land type of your choice until end of turn.

Lost Soul

Raiding Nightstalker

Swamp

Tendrils of Corruption

Tendrils of Corruption deals X damage to target creature and you gain X life, where X is the number of Swamps you control.

Island

Goblin Flotilla

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
At the beginning of each combat, unless you pay {R}, whenever Goblin Flotilla blocks or becomes blocked by a creature this combat, that creature gains first strike until end of turn.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Grayscaled Gharial

Quag Vampires

Multikicker {1}{B} (You may pay an additional {1}{B} any number of times as you cast this spell.)
Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Quag Vampires enters with a +1/+1 counter on it for each time it was kicked.

Slimy Kavu

{T}: Target land becomes a Swamp until end of turn.

Dirtwater Wraith

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
{B}: Dirtwater Wraith gets +1/+0 until end of turn.

Tidal Warrior

{T}: Target land becomes an Island until end of turn.

Woodlot Crawler

Forestwalk (This creature can't be blocked as long as defending player controls a Forest.)
Protection from green

Benthic Djinn

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
At the beginning of your upkeep, you lose 2 life.

Bog Wraith

Expedition Map

{2}, {T}, Sacrifice this artifact: Search your library for a land card, reveal it, put it into your hand, then shuffle.

Odylic Wraith

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Whenever Odylic Wraith deals damage to a player, that player discards a card.

Arcane Signet

Wrexial, the Risen Deep

Islandwalk, swampwalk (This creature can't be blocked as long as defending player controls an Island or a Swamp.)
Whenever Wrexial, the Risen Deep deals combat damage to a player, you may cast target instant or sorcery card from that player's graveyard without paying its mana cost. If that spell would be put into a graveyard, exile it instead.

Drowned Catacomb

Drowned Catacomb enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Wayfarer's Bauble

{2}, {T}, Sacrifice Wayfarer's Bauble: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Bog Smugglers

Rishadan Dockhand

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
{1}, {T}: Tap target land.

Jinx

Target land becomes the basic land type of your choice until end of turn.
Draw a card at the beginning of the next turn's upkeep.

Orcish Farmer

{T}: Target land becomes a Swamp until its controller's next untap step.

Spreading Seas

Enchant land
When Spreading Seas enters, draw a card.
Enchanted land is an Island.