The Lore book gives more background about him as well. I'm kind of torn about it though. Part of me wants us to drive Regula back to the Emperor and that forces the Emperor to have him executed to show that he's not held back by personal relationships regardless of their nature. Of course Regula would probably accept that as the price of his failure.
Then again, actually killing Regula would also be fun. He's managed to escape me a few times, I've been really wanting to rectify that situation. But considering how the VIth Legion has appeared in the Warring Triad storyline so far, my theory is either that he'll get tempered by Zurvan or we'll deal with him in a solo instance.
But now I'm trying to remember something. What was the order of release for seph -> regula instance -> goddess? 3.2 -> 3.3 -> 3.4? Either way, I'm convinced we'll deal with Regula one way or the other by the end of the Warring Triad story.