The Fraxinos Entity was an incorporeal creature that evolved on Fraxinos. It was capable of possessing bodies with the help of a psychograft. The Fraxinos Entity possessed the body of Natalie Sharrocks and destroyed a Chelonian breeding planet.
It also attempted to possess the body of Baxter and commit another crime, but was stopped by the Tenth Doctor. Once the psychograft was made illegal on Fraxinos, the Entity had no way of possessing people. (PROSE: The Body Bank)