Trodos was a human colony world.
Civilisation existed on Trodos for six million years before the invention of the Trods. (AUDIO: Cold Fusion) In 2066, MacTaggart constructed the Trods to give himself power over the other colonists and used them to enslave everyone. When the First Doctor, John and Gillian arrived on Trodos, they deactivated the Trods and freed the slaves. (COMIC: The Trodos Tyranny)
Someday after 2050 K9 was free falling in space and awaited any passing vessels that had been accused of being a stow-away on the flagship of the Trodos Empire. Later he entered a Sporraxx space ship. (COMIC: Short Circuit)