my advice here Grip (which i am sure you would do anyway) is to ask politely is he tries to pull anything that seems out of the ordinary.
the special rules for the sisters seem to be rather complex to the outside point of view - you would be well within your rights to ask to read the rules - apart from anything else, he may simply not 'get' the rules himself and a third person point of view may just be what he needs.
i the meantime if you happen accross anything that you need clarifying, the guys here know their stuff
aside from ID anyway - he still deep strikes Seraphim
