The Rhodians were a humanoid race on Rhodia. They were at war against the Quill.
Biology
In their natural state, male Rhodians were grey-skinned, and had pointy ears and spikes along the jawline. (TV: For Tonight We Might Die)
Culture
The Rhodians were a cultured, learned society. Homosexuality was more accepted than on 21st century Earth. (TV: For Tonight We Might Die)
History
According to Miss Quill, the Rhodians ate up all the planet's resources, including that of the Quill. They tried to help the Quill, but in the process made them so dependent that they could never recover. (TV: For Tonight We Might Die)
The two species were eventually at war with each other, when the Shadow Kin arrived, and destroyed them all. All but one of the Rhodians were destroyed by the Shadow Kin: Charlie, their prince, who was brought by the Twelfth Doctor to Coal Hill Academy. (TV: For Tonight We Might Die)