Magus of the Coffers

{2}, {T}: Add {B} for each Swamp you control.

Avalanche

Barbarian Guides

{2}{R}, {T}: Choose a land type. Target creature you control gains snow landwalk of the chosen type until end of turn. Return that creature to its owner's hand at the beginning of the next end step. (It can't be blocked as long as defending player controls a snow land of that type.)

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.

Legions of Lim-Dûl

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

Everglades

Everglades enters tapped.
When Everglades enters, sacrifice it unless you return an untapped Swamp you control to its owner's hand.
{T}: Add {C}{B}.

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.

Wild Ox

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

Arcum's Weathervane

{2}, {T}: Target snow land is no longer snow.
{2}, {T}: Target nonsnow basic land becomes snow.

Contaminated Ground

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

Warthog

Defile

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

Stern Judge

{T}: Each player loses 1 life for each Swamp they control.

Karma

At the beginning of each player's upkeep, Karma deals damage to that player equal to the number of Swamps they control.

Crusading Knight

Protection from black
Crusading Knight gets +1/+1 for each Swamp your opponents control.

Royal Decree

Cumulative upkeep {W} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Whenever a Swamp, Mountain, black permanent, or red permanent becomes tapped, Royal Decree deals 1 damage to that permanent's controller.

Bog Smugglers

Cabal Coffers

Dakmor Sorceress

Dakmor Sorceress's power is equal to the number of Swamps you control.

Blistergrub

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

Arctic Foxes

Arctic Foxes can't be blocked by creatures with power 2 or greater as long as defending player controls a snow land.

Gwyllion Hedge-Mage

When Gwyllion Hedge-Mage enters, if you control two or more Plains, you may create a 1/1 white Kithkin Soldier creature token.
When Gwyllion Hedge-Mage enters, if you control two or more Swamps, you may put a -1/-1 counter on target creature.

Zombie Musher

Snow landwalk (This creature can't be blocked as long as defending player controls a snow land.)
{S}: Regenerate Zombie Musher. ({S} can be paid with one mana from a snow source.)

Nightcreep

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

Bubbling Muck

Until end of turn, whenever a player taps a Swamp for mana, that player adds an additional {B}.

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.

Nightmare Lash

Equipped creature gets +1/+1 for each Swamp you control.
Equip—Pay 3 life. (Pay 3 life: Attach to target creature you control. Equip only as a sorcery. This card enters unattached and stays on the battlefield if the creature leaves.)

Crypt Ghast

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Whenever you tap a Swamp for mana, add an additional {B}.

Cyclopean Giant

When Cyclopean Giant dies, target land becomes a Swamp. Exile Cyclopean Giant.

Infernal Harvest

As an additional cost to cast this spell, return X Swamps you control to their owner's hand.
Infernal Harvest deals X damage divided as you choose among any number of target creatures.

Nirkana Revenant

Whenever you tap a Swamp for mana, add an additional {B}.
{B}: Nirkana Revenant gets +1/+1 until end of turn.

Anurid Murkdiver

Kormus Bell

All Swamps are 1/1 black creatures that are still lands.

Cabal Stronghold

{T}: Add {C}.
{3}, {T}: Add {B} for each basic Swamp you control.

Liliana of the Dark Realms

+1: Search your library for a Swamp card, reveal it, put it into your hand, then shuffle.
−3: Target creature gets +X/+X or -X/-X until end of turn, where X is the number of Swamps you control.
−6: You get an emblem with "Swamps you control have '{T}: Add {B}{B}{B}{B}.'"

Angry Mob

Trample
During your turn, Angry Mob's power and toughness are each equal to 2 plus the number of Swamps your opponents control. During turns other than yours, Angry Mob's power and toughness are each 2.

Mutilate

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

Bog Raiders

Blanket of Night

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

Farbog Explorer

Squelching Leeches

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

Corrupt

Corrupt deals damage to any target equal to the number of Swamps you control. You gain life equal to the damage dealt this way.

Cyclopean Tomb

{2}, {T}: Put a mire counter on target non-Swamp land. That land is a Swamp for as long as it has a mire counter on it. Activate only during your upkeep.
When Cyclopean Tomb is put into a graveyard from the battlefield, at the beginning of each of your upkeeps for the rest of the game, remove all mire counters from a land that a mire counter was put onto with Cyclopean Tomb but that a mire counter has not been removed from with Cyclopean Tomb.

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.

Urborg, Tomb of Yawgmoth

Cold Snap

Cumulative upkeep {2} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
At the beginning of each player's upkeep, Cold Snap deals damage to that player equal to the number of snow lands they control.