Rethdurk von Kark was a Great Knight aristocrat and captain who was known for his loyalty to the Great Knights and an uncanny "sixth sense" which allowed him to detect danger before it emerged, hence he was usually in charge of reinforcing groups. This sixth sense came from a spirit known as Tarramiso-Katos, which had partially possessed him.
Rethdurk's father was from Riff Island, while his mother originated from Westwind. Given both of their privileged upbringings, they were both effectively aristocrats, and Rethdurk was their only child. When he was 13, Rethdurk was diagnosed with being bipolar by doctors when his family became increasing worried about his sometimes erratic behaviour, which contrasted with his usual calm, sarcastic manner. In truth, Rethdurk had been partially possessed by an Esoteric Spirit named Tarramiso-Katos, a student of the Esoteric mage Tarconencis. Tarramiso had been dormant and regaining energy for many years, and found the young Rethdurk and was able to partially possess him. After a hard-fought mental struggle over several years, Rethdurk effectively integrated Tarramiso as a part of him, and used the latter's enhanced senses to guide him. By the age of 16, he could even shape-shift, but he successfully hid Tarramiso from the rest of the world. As an aristocrat, he was able to join the army rapidly as a cavalry officer, but he soon found that Tarramiso was capable of giving him enhanced speed, strength and senses and therefore preferred fighting on foot.