In Norse mythology, Ull ("glory") was a son of Sif though not by her husband, Thor, and styled god of the snowshoe, god of the bow, hunting-God, god of the Shield. A shield is called the 'ship of Ullr'. Ullr lived in a hall called Ydalir 'Yew-dales'.
In Saxo Grammaticus' Danish History, Book III, where gods appear euhemerized as powerful humans, Ull, under the name Ollerus, is described as "such a cunning wizard that he used a certain bone, which he had marked with awful spells, wherewith to cross the seas, instead of a vessel; and that by this bone he passed over the waters that barred his way as quickly as by rowing."
When Odin was exiled, Ollerus was chosen to take his place. Ollerus ruled under the name Odin for ten years until the true Odin was called back, whereupon Ollerus retired to Sweden where he was slain by Danes.
The appearance of Ull's name in numerous Norwegian place names suggests Ull had a religious importance far greater than would appear from the scanty surviving textual references.
Ullr seems to be a variant of a wide-spread god of the bow, plague and the wild represented in Greece by Apollo, among northwest Semites by Resheph/Rashpu, in the Vedas by Rudra and possibly in Welsh by Arawn.
Alternatives: Ullr (Old Norse), Vuldr, Wulder, Ulr (New Norse)
Some Modern Inventions:
In Victor Rydberg's idiosyncratic Teutonic Mythology Ull is the son of Sif and Egil-Orvandill, half-brother of Swipdag - Odr, nephew of Weland Smith and a cousin of Skadi. His father Egil was the greatest archer in the mythology, and Ull follows in his father's footsteps. Ull helped Swipdag-Erik rescue Freya from the giants. He also ruled over the Vans when they held Asgard during the Van-As War.