Rhodia was a planet, according to Charlie, "more beautiful than you could ever believe", "paradise". It was home to three billion people from two dominant species: the Rhodians and the Quill. (TV: For Tonight We Might Die)
The Rhodians and Quill warred with each other, though each side remembered the reasons for the conflict differently. The Rhodians claimed the Quill mismanaged their economy and were resentful of the Rhodians' success; the Quill claimed the Rhodians ate up all the planet's resources, including that of the Quill. The Rhodians tried to help the Quill, but in the process made them so dependent that they could never recover.
The less numerous Quill rebels used war tactics described by the Rhodians as terrorism, though they thought of themselves as freedom fighters. The Rhodians won, ending the Quill's attacks and enslaving their captured leader, Miss Quill, with an arn, forcing her to become the protector of the Rhodian prince, Charlie.
While the inhabitants of Rhodia were busy fighting amongst themselves, the Shadow Kin arrived and killed all three billion, Rhodian and Quill alike. Charlie and Miss Quill were the only survivors - the last of their respective species. They were rescued by the Twelfth Doctor and brought to Coal Hill Academy in 2016. (TV: For Tonight We Might Die)