A rather prominent figure in Welsh mythology, Arawn is responsible for chasing down lost souls with his hounds and is the (early) king of the Otherworld.
Usually seen with grey hounds, and could be riding a white horse. Nothing else is associated with him except for the colors associated with the Otherworld: white, grey, and sometimes black.
Arawn was the first king of the Celtic Otherworld, but later was superseded in the myths by Gwyn ap Nudd. The Hounds of Arawn could be seen riding through the skies in any season but summer. The Hounds chase wandering spirits back to the Otherworld, Annwn (pronounce roughly “ah-noon”).
Arawn was instrumental in elevating the status of the mortal Pwyll, Lord of Dyfed (prnounced roughly “doo-ved”). The two met when Pwyll chased away Arawn’s hounds bringing down a stag and sent his own hounds on the stag. Arawn was understandably rather offended, and as payment as Pwyll to trade places with him for one year and defeat Arawn’s enemy Hafgan. Pwyll agreed, and wore Arawn’s likeness and ruled over Annwn for a year, while Arawn wore Pwyll’s likeness and ruled Dyfed.
At the end of the year, Pwyll had defeated Hafgan. Arawn and Pwyll became good friends not only for Pwyll’s victory, but because Pwyll had slept chastely next to Arawn’s wife the entire year (Pwyll was not yet married, so Arawn had no like temptation). Pwyll was happy because his realm had never flourished so well as it had under the care of Arawn. When Pwyll returned, he gained the name of Pwyll Pen Annwn, and is considered a lord of the Otherworld.
Arawn’s wife is not named, and it’s not known if they had any children. What is known is that the friendship between Annwn and Dyfed continued long after Pwyll’s death.
Light and Dark Sides
Although there is a pretty good description of Arawn and his personality, it’s difficult to say exactly where he falls on the spectrum. I’d say he’s a very grey character. He brings back the souls that get lost or wander and returns them to their place in Annwn. In that respect, he and his hounds are guiders of the soul, a psychopomp. He could also be considered a god of death.
Since he is the king of the Otherworld, there is a great deal of mystery and magic associated with Arawn. The Otherworld is a strange and mysterious place–clearly seen in its name, the Other World. It is Other, and therefore unknowable. Arawn, as lord of that realm, would carry many of those same qualities with him. He is Other himself, a guider of souls but also the unknowable mystery of the soul, if that makes sense.