Duel on Ossus

In 4,400 BBY, Jedi apprentice Freedon Nadd engaged his Master Matta Tremayne in a lightsaber duel on the planet Ossus. Furious at his failure to be promoted to the rank of Jedi Knight, Nadd declared himself one nonetheless, and Tremayne challenged him to prove it to her through lightsaber combat. The duel ended with Nadd slaying Tremayne, an act which precipitated his subsequent fall to the dark side of the Force.