First of all, mystery author, I love that Severus was Lewis. This is a small detail that made me smile. While I do enjoy stories where Severus has some other emperor's name, to me he's a simple man. Lewis is a fine name, and I'm sure it's common in England. Again, small detail but one that I liked.
Your notion of soul magic vs. soul mates was mature for a mature reader. It's sweet to read about soul mates, but sometimes the adult in you wants something meatier to hold on to. Yes, this is a story about magic, but the relationship here is based more in reality. Hats off!
And of course the sex. *sighs* Yes, the sex was incredibly hot. I like, but do not love, bottom!Harry, but I really liked what you did with him here. You made him a man (a gay man) and not a boy, not small or weak in the bedroom. That made the bottom!Harry that much better for me.
All in all, a wonderful story. Veridian is a lucky girl.