The Thara are a primitive, methane-breathing race native to the swamp planet Golrandonvar. At some point in their history, their homeworld was invaded by Human colonists who attempted to alter the atmosphere to make it inhabitable and wipe out the Thara in the process, regarding them as inferior life forms. The Eleventh Doctor helped them resist the invasion and sent the colonists away to another, uninhabited world with a supply of Heligan Trees to make it inhabitable. Rather than colonizing that new world, however, the Humans cultivated an enormous Heligan Tree and built an entire civilization within it, eventually giving rise to a unique culture with a deep and historical hatred for the Doctor.
- The Roots of Evil, by Philip Reeve (2013)