[Cainehill]

I'm actually guessing not, simply because once cast, Astral Shield is semi-static : MR only seems to come into play when a spell / effect is cast, where AS is more of a constant effect. My guess is that it's more like, mmm, regen or fireshield : the spell effect goes by the level of magic in the path, and probably gets shafted when the caster shapeshifts or otherwise loses magic ability.

(Which, fwiw, seems bogus to me : If a dragon casts fire shield in human form, Fire Magic 9, the fire shield should be at that strength from when it was cast, not taper off when the caster changes shape and loses magic ability. Ditto Regen, etc. Oh - and if a Pythium mage casts Fire Shield at F7 from communicants, does _his_ FS go down in strength as communicants die?)