Island

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.

Boggart Loggers

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

Raiding Nightstalker

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

Crumbling Necropolis

This land enters tapped.
{T}: Add {U}, {B}, or {R}.

Mutilate

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

Lost Soul

Slimy Kavu

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

Tolaria West

This land 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.)

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.)
This creature enters with a +1/+1 counter on it for each time it was kicked.

Bog Wraith

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.

Koth's Courier

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

Mountain

Anurid Murkdiver

Blistergrub

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

Rootwater Commando

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

Arcane Signet

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

Contaminated Ground

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

Sewerdreg

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

Merfolk Spy

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

Moor Fiend

Sol Ring

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.)

Smoldering Marsh

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

Maestros Theater

When this land 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.

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.

Slinking Serpent

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.

Chasm Skulker

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

Dirtwater Wraith

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

Marsh Goblins

Evolving Wilds

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

Tidal Warrior

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

Dragonskull Summit

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

Orcish Farmer

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

Defile

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

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.

Yavimaya, Cradle of Growth

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

Bog Raiders

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.

Woodlot Crawler

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

Bog Tatters

Shimmering Mirage

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

Grayscaled Gharial

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 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.

Expedition Map

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

Reef Shaman

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

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 this creature. (Activate only as an instant.)

Mystic Compass

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

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.)

Blanket of Night

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

Tideshaper Mystic

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

Thada Adel, Acquisitor

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

Evil Presence

Whispering Shade

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

Terramorphic Expanse

Lingering Mirage

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

Slithery Stalker

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

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.

Viscid Lemures

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

Bog Smugglers

Tainted Well

Enchant land
When this Aura enters, draw a card.
Enchanted land is a Swamp.

Filth

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

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 this creature blocks or becomes blocked by a creature this combat, that creature gains first strike until end of turn.

Swamp

Wayfarer's Bauble

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

Sea's Claim

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

Dream Thrush

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

Odylic Wraith

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

Rishadan Dockhand

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

Command Tower

Plague Beetle

Spreading Seas

Enchant land
When this Aura enters, draw a card.
Enchanted land is an Island.

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.)

Drowned Catacomb

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