We'll Atmos doesn't talk at least not in a way we understand. I can't remember if Cait or someone else calls them an avatar or not. Also a little fuzzy if one of the spite wardens calls Cait one or not or if the bad Cait calls themselves it. Though Atmos is at least summoned by Lady Lilith to eat what is left of lilliset in front of us. I guess they are part of the Odin Alexander group of other.