Sulumians were a species which resided in the eighth dimension. They resembled bipedal mules with smooth grey skin like a dolphin's, and possessed glowing red eyes.
Around 317,000 AD, humans encountered the Sulumians in their domain in the eighth dimension. To prevent this from happening, Thorgan travelled back in time to divert Earth's history. (PROSE: The Gallifrey Chronicles [+]Lance Parkin, BBC Eighth Doctor Adventures (BBC Books, 2005).)