Face Heel Turn: In the 2012 game, he is introduced as a good knight, who is sent to track down a vampire who has been kidnapping and killing villagers. He loses, gets turned into a vampire and becomes evil.
Darth Vader Clone: A robust character using a sword? Check. Wearing black armour that completely hides his face? Check. Dark Magic? Check. Deep voice? Check. Definetely a Darth Vader clone.
Talking to Himself: He is voiced by Zsolt Tóth, the creator of the game who also voiced Stephánus Tavilrond, and the vampire who turned Dermaglen. In the first mission where the player controls the still-good Dermaglen, this trope is played quite straight during the encounter with the vampire.
What Could Have Been: As the 2012 game was intended to have Multiple Endings - based off the player's choice between Good and Evil - he was meant to be a playable character in case the player turned to the Dark Side.