Thread by @CoelingAurochs

*Thread*
Osla Gyllellfawr, The great-knife of the Saxons? Or warrior in Arthur's warband?

Osla shows up in two early Welsh tales, "Dream of Rhonabwy" and "Culhwch and Olwen". In 'Culhwch' he is a member of Arthur's retinue, and is known for his great-knife "Bronllafn" which was so large it could be used as a bridge.

He even participates in the hunt for the monstrous boar Twrch Trwyth, dying while crossing the Severn, dragged into the depths by the sheath of his great knife which filled with water.

Osla appears again, this time in the "Dream of Rhonabwy", not as part of Arthur's warband, but as his enemy, awaiting a fight at the famed Battle of Badon.

Some have proposed that this is Offa of Mercia, the 8th century king famed for building Offa's Dyke, a great defensive earthwork designed to keep the Welsh hemmed into their own country. I would however propose that Osla is inspired by an earlier figure.

Osla is none other than Octa of Kent. Octa was either the son of Hengist, or his grandson via Oisc, although I find son to fit the accepted chronology better. Octa is known for raiding Scotland on behalf of Vortigern before becoming King of Kent.

This is likely a memory of his role as a mercenary or Foederati chieftain for one of the Northern Kings, Ceneu ap Coel specifically, eventually leading to the settlement of Deira, and Octa's expulsion at the hands of Mar ap Ceneu.

From there Octa heads back south becoming king upon his father's death, and maybe even becoming an enemy of Arthur, specifically at Badon? I have proposed a more central location for Badon before, you can read about that here.
aurochs.substack.com/i/64282755/bad…

It would not be out of the question for this to be an incursion into Powys from a Germanic coalition headed by Octa. Liddington Castle is a strong possibility as well, and easily within Octa's reach.

I think this memory of Octa as both ally and enemy of Arthur are quite interesting, especially when considering a Northern Arthur. Octa likely fought alongside Mar ap Ceneu in his youth, ultimately being expelled from the north by him when relations soured.

Years after his expulsion from the North, he encounters Mar's son Arthuis, who then defeats him at Badon. This leads to Octa being remembered as an ally of the British, and an enemy, as Osla "Great-Knife" (Seax), a 'Saxon' in Brythonic service, turned enemy.