Rivesh Mantilax was the husband of Seruba Velak.
Rivesh worked in genetic warfare for his kind. He was the designer of a genetic weapon that would kill all Viperox in the universe, to which the Tenth Doctor objected. When the Viperox went to war with his kind, his side lost. His wife, Seruba Velak, had already crashed in Roswell in 1947. As soon as he could, Rivesh went to find her. When his ship was shot down by the US Military near Area 51 in 1953, he was saved by Night Eagle and hidden in a cave. In 1958, Night Eagle took the Doctor, Cassie Rice and Jimmy Stalkingwolf to see Rivesh, who told them his story. Just moments afterwards, Colonel Stark walked in and tried to arrest him.
Stark locked up Rivesh in Dreamland, separated from Seruba by a panel of glass. When his enemy Lord Azlok escaped from the Area 51 base, he attacked Rivesh. Seruba and the Doctor later went to Seruba's ship to find a cure for him. Seruba revived Rivesh and he activated the device, which the Doctor modified with his sonic screwdriver to emit a high-pitched noise, amplified by the TARDIS, that could only be heard by the Viperox, who fled from Earth back to Viperon. Rivesh and his wife returned to their own home. (TV: Dreamland)