Cissa

A Saxon warrior who arrived in Britain in 477 with his father, Ælle, and his two brothers, Cymen and Wlencing.

Upon landing in Cymensora, they defeated the Britons and, in 492, fought and won another battle against the Britons at Andredsceaster.

The Chronicle does not link him to Arthurian tradition, but, assuming that Ambrosius and Arthur existed, Cissa would have been their contemporary (and opponent).