Urborg, Tomb of Yawgmoth

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

Angel of Destiny

Flying, double strike
Whenever a creature you control deals combat damage to a player, you and that player each gain that much life.
At the beginning of your end step, if you have at least 15 life more than your starting life total, each player Angel of Destiny attacked this turn loses the game.

Selfless Squire

Flash
When this creature enters, prevent all damage that would be dealt to you this turn.
Whenever damage that would be dealt to you is prevented, put that many +1/+1 counters on this creature.

Crusading Knight

Protection from black
This creature gets +1/+1 for each Swamp your opponents control.

Lightmine Field

Whenever one or more creatures attack, this enchantment deals damage to each of those creatures equal to the number of attacking creatures.

Dingus Staff

Whenever a creature dies, this artifact deals 2 damage to that creature's controller.

Rune-Tail's Essence

Prevent all damage that would be dealt to creatures you control.

Rune-Tail, Kitsune Ascendant

When you have 30 or more life, flip Rune-Tail.

Rune-Tail, Kitsune Ascendant // Rune-Tail's Essence

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.

Blessed Sanctuary

Prevent all noncombat damage that would be dealt to you and creatures you control.
Whenever a nontoken creature you control enters, create a 2/2 white Unicorn creature token.

Quietus Spike

Equipped creature has deathtouch.
Whenever equipped creature deals combat damage to a player, that player loses half their life, rounded up.
Equip {3}

Darien, King of Kjeldor

Whenever you're dealt damage, you may create that many 1/1 white Soldier creature tokens.

Caltrops

Whenever a creature attacks, Caltrops deals 1 damage to it.

Scytheclaw

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.
Whenever equipped creature deals combat damage to a player, that player loses half their life, rounded up.
Equip {3}

Karma

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

Stern Judge

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

Eight-and-a-Half-Tails

{1}{W}: Target permanent you control gains protection from white until end of turn.
{1}: Target spell or permanent becomes white until end of turn.