I can't remember the title to the book but it was about these guys who had been taken from different time lines and thrown into a nether world of sorts. They all had escaped and were in the modern world fighting to make sure they weren't found and taken back. I do remember that the main guy in the first book had been an Ostrogoth his name starts with an O and he uses rune stones.
As per the link from that the OP put in his answer
Author: Ewing, Lynne.
Series: Sons of the dark ; 1
Summary: Having escaped from Nefandus, a parallel universe where he was made an immortal slave, fifteen-year-old Obie must return to retrieve his mother's rune stones in order to fulfill his destiny in modern-day Los Angeles as one of the four Sons of the Dark.