Frederick

1. Frederick
   Frederik

   The King of Friesland and the Frisians, according to the Alliterative Morte Arthure, who allied with Mordred during the latter’s rebellion against Arthur.

   
   

2. Frederick de Telramund
   Friedrich of Dundramunt

   A knight who wanted to take Elsa of Brabant's kingdom from her. No one dared to fight him - he had a reputation to have killed a dragon in Stockholm, Sweden. He was defeated by Lohengrin.