Tomb of the Spirit Dragon - Commander Masters: Extras (Uncommon) [XCMM-1048]

Tomb of the Spirit Dragon is a land from Commander Masters that taps for colourless mana and has an activated ability allowing you to gain life based on the number of colourless creatures you control. This can be a solid source of life gain in colourless creature strategies, particularly in decks focused on Eldrazi or other colourless threats. However, it doesn't produce coloured mana, so it's best suited for mono-colour or colourless builds.