In Welsh tradition Arawn was the name of the King of Annwfn, the Welsh otherworld, in the non-Arthurian tale of Pwyll, but it may also have been the name of Urien’s brother in Welsh legend before Geoffrey wrote his Historia.
After clashing with Pwyll during a hunting incident, the two warriors became friends and agreed to exchange countenances, kingdoms, and wives for a year. Pwyll, however, refused to take advantage of the situation and sleep with Arawn’s wife. Arawn’s mortally enemy, Hafgan, was killed by Pwyll.
R. S. Loomis thought that a number of Arthurian characters showed Arawn’s influence, including the Green Knight and Orguelleuse. In a Welsh version of Geoffrey of Monmouth, Arawn becomes the counterpart of Angusel, Urien’s brother. Arawn may therefore be identical to Aron, Urien’s brother and Arthur’s knight in the Triads.