Ossa Cylellaur
A "historical" military figure, a leader of the Saxons and Arthur's opponent at the battle of Badon Hill.
Ossa does not appear, at least by his name, in Malory or the Vulgate, but Glennie seems to try to connect him with Gallehault (Duke Galeholt?) - a connection which need not concern us here, except as it may give grounds for making Duke Galeholt a Saxon.