So this is something I've been thinking about for a while. Masael requires a host to consistently and directly interact on the mortal plane of existence, they are rooted, as it were. The bond has symbolic properties, it is a union between their two species, a partnership so they can work together to protect the world from the darkness trying to consume it. Mas and her host bonded twice (Mas left when there was no longer a threat, the problem "fixed"), the second time, however, things went badly and they fused together. Her host was, essentially, consumed. I think it's a fairly major point of regret for Mas.

I could go on, but I feel I'm rambling and being boring. I haven't come up with a name for the host yet though.

Um. But yeah.