Shadow of Angels by Kathryn Ann Kingsley

The first time I died was November 1st, 1945. That might’ve been the first time, but it certainly wasn’t the last.
My name is Veil, and my life has been far from normal. Everything I thought I knew about myself had been a lie. Every single thing. Turns out, I had been in the care of a cult dedicated to a King in Hell and fallen archangel.
But after learning the truth of who—or what—I was, I devoted my life to stopping them and everyone like them.
Which is why when I learned that Boston was under siege from an occult society who was slaughtering innocents, I had no choice but to come and stop them. Even if it meant it would take me piece by piece through that past I’d spent seventy years trying to avoid—and right into the presence of the archdemon I’d been running from for so very long. Asmodeus.
Just when I thought things could not get worse, I realized once more that I had no clue what was coming next…