Who Is The Invisible Prince?

In this (probably 18th-century) fairy-tale, Prince Leander has a claim to the throne but can't support it. Instead he serves the actual heir, the deformed and evil Prince Furibond. Furibond's jealousy of his handsome and loyal companion turns to murderous hatred when Leander is mistaken for the prince, and Furibond for the court dwarf, by some visitors. Leander is exiled and an attempt made on his life. In his loneliness he befriends and feeds a white adder, which one day turns into a fairy and rewards his kindness by giving him the power to go wherever he wishes, and a cap of invisibility. He uses these powers, first to avenge himself on Furibond, and then to find himself a wife. He does this by gaining access to the home of a princess who has been brought up to hate all men, and is kept in a locked castle. Once they meet, she falls in love with him and they are married.