The godly son of the sea, Manannán, is one of the most prominent characters of the old Celtic stories. Unlike other better known sea-gods like Poseidon, Manannán always seemed to be a much more light-mooded figure, less enraged and more playful. He is attributed a myriad of roles in the old legends; from guardian of the Otherworld to Lawmaker of the gods.
What I particularly like about him is that he seems to be exist on and live by different rules than the rest of his heavenly tribe, seemingly appearing and disappearing at his own leisure to bestow gifts or play tricks; kinda doing his own thing while everybody else is busy and hung about with this battle or that cattle raid.
Manannán was master of a good number of magical items, his most well-known being his magical cloak. This misty mantle could cast an enshrouding veil of concealment and illusion. When the Tuatha Dé Danann retired underground after their battle with the sons of Mil, Manannán cast this magic mist to hide them and their abodes from the eyes of mortal men.