Urborg, Tomb of YawgmothHow it works & interactions with other cards

The Transformation Process

While Urborg, Tomb of Yawgmoth is on the battlefield, every land currently in play gains the land type 'Swamp' in addition to its existing types. This means that a basic Forest remains a Forest but becomes a Forest Swamp, while nonbasic lands like a Desert become a Desert Swamp. Crucially, any land that becomes a Swamp automatically gains the intrinsic mana ability: '{T}: Add {B}.' This does not remove any existing abilities the land already had; it simply adds a new way to tap for mana.

Timing and Zones

Urborg, Tomb of Yawgmoth only functions while it is on the battlefield. It is not a Swamp while it is in your hand, library, or graveyard. Furthermore, it only affects other lands that are already on the battlefield. You cannot use a card that searches for a Swamp to find a non-Swamp land from your deck just because Urborg is in play. Its ability is a continuous effect that applies as long as Urborg remains an active permanent on the field.

Interaction with Type-Setting Effects

A common mistake involves how Urborg interacts with effects that remove abilities. If an effect sets Urborg to a specific basic land type (like a Mountain) and explicitly states it is not 'in addition to its other types,' Urborg will lose its ability to turn other lands into Swamps. This holds true regardless of which land entered the battlefield first. If Urborg loses its text box, the world stops being a Swamp.

Strategic Deployment

Because Urborg is a legendary land, you cannot have two copies of it on your side of the field simultaneously; the Legend Rule would force you to put one into the graveyard. However, its effect is symmetrical, meaning your opponents also gain the ability to produce black mana. You should play it when you need to fix your mana or when you are prepared to capitalize on 'Swampwalk' abilities or cards that scale based on the number of Swamps you control.

Interaction examples

Expanding Color Identity

Command Tower

Step 1: You have both lands on the battlefield. Step 2: Urborg, Tomb of Yawgmoth applies its effect, making Command Tower a 'Land - Swamp'. Step 3: Even if your Commander does not have Black in its color identity, Command Tower now has the ability '{T}: Add {B}' because it is a Swamp. You can now tap it for Black mana or its original ability.

Opponent Interaction

Exotic Orchard

Step 1: Your opponent controls Exotic Orchard and you control Urborg, Tomb of Yawgmoth. Step 2: Urborg turns your opponent's Exotic Orchard into a Swamp. Step 3: Your opponent can now tap their Exotic Orchard for Black mana. Step 4: If you play your own Exotic Orchard, it can now tap for Black mana because your opponent's land 'could produce' Black mana due to the Swamp type granted by your Urborg.