Lifetap

Whenever a Forest an opponent controls becomes tapped, you gain 1 life.

Urborg, Tomb of Yawgmoth

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

Roots of Life

As Roots of Life enters the battlefield, choose Island or Swamp.
Whenever a land of the chosen type an opponent controls becomes tapped, you gain 1 life.

Yavimaya, Cradle of Growth

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

Cabal Coffers

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