 Complete the following phrase:  Octa may appear in Welsh Arthurian literature as Osla Bigknife, though this character may be better identified with Offa of Mercia. This Osla figures in two medieval prose tales, Culhwch and Olwen c. 1100 and The Dream of Rhonabwy 12th- or 13th-century. In Culhwch he is a member of King Arthurs retinue; he is named in a list of Arthurs followers, and his weapon Bronllavyn Short Broad, which is wide enough for Arthurs army to use as a bridge, is described. Osla later participates in the hunt for the great boar Twrch Trwyth, during which he nearly drowns when the sheath of his great knife fills with water. In Rhonabwy Osla is Arthurs opponent at the 