Hytheriax VII

Merlin once sent Galahad, Gawain, Bedevere and Agravaine to his sister Ganeida for magical aid in fighting Morch'aliach because he, himself, had to go to "a party on Hytheriax VII". The knights were not sure where Hytheriax VII was located, although Bedevere guessed it might have been in Gaul. (PROSE: A Honeycomb of Souls)