"Same reason you were, really... a failed attempt to rescue mortals." She sighs, softly. "There were seven of us, when we started. A lucky number, it was supposed to be. Three died the first day, two were captured shortly after, and the remaining... I don't know. We were separated, by a portal and fighting... I don't know what ever happened to him. When I was cornered, I managed to find a place to hide, and erect my barrier, enhancing it over the first year I was there. As you saw, it was almost impenetrable... and I figured no demon would ever find something as pure as you, in the hopes I could hold out, until another raid found me. But... this was certainly the preferable outcome; at least I won't be used for evil."