House was a malevolent, mysterious entity which lived in a small space outside of the universe. House existed as an intelligence in a space-time rift. His body was an asteroid-sized celestial object. At the time of his encounter with the Doctor, he implied that he was at least half a million years old. House's energy was mostly green. When he controlled the Tardis, it's turquoise glass turned bright green, and green swirls went round the Tardis.