Seth is one of the oldest humans in Oberin, having been alive ever since the First Era. It is because of his intervention that humanity managed to survive the Black Plague. The mentor of Evers, he is a powerful practicioner of Black Magic. He once required a special stone to live called the Verma Stone.
Seth was the one who created the original Pure Crystal Machine, which allowed for mass transportation around Oberin with the use of purified crystals. On the other hand, Seth is notorious for meddling with the portals in Oberin. After the War of the Poison Forges in 425, he accidentally disabled the entire portal system. Then, around the Sleeping Moon of Year 428, he tried to reactivate the fire portal using the original Ice Crystal as a catalyst. It didn't work, and all the portals stopped functioning again. He finally got the fire portal working in 433, opening the way to Hell (and inadvertently causing a volcanic explosion).