It looks like Lucian banished Damian to Nemesis by stabbing him in the chest with a two-hander, which is an original way of doing things. At least that's what they show in the paintings. Also, in DOSEE you can meet with the guys from Nemesis searching for imps and they mention that they serve the demons which indicates that Nemesis is just a demon homeworld according to the new lore, and not the dimention they occupied because of Damian.