Gog and Magog, also known as the Gomagog, were a group of Great Old Ones. (PROSE: Divided Loyalties, AUDIO: The Archive) In Earth's mythology they were known as giants. (TV: The Stones of Blood).
The Gomagog were powerful interdimensional beings that have destroyed many worlds. Some believed them to be a dark emanation of the Archive. (AUDIO: The Archive)
The Fourth Doctor believed that the myth of Gog and Magog was inspired by the Ogri of the Nine Travellers. (TV: The Stones of Blood). He also encountered an individual called Magog in a parallel universe. (COMIC: The Iron Legion)