This is a sad tale! So have the angel/celestials completely turned theirs backs on their imprisoned brethren? There has got to be a way to liberate or at least puts to rest, the souls of those devas.
Well, it's supposed to be resolved by adventures, otherwise now that it has become a very important site to the tanar'ri it would take a celestial army to liberate them. Also it would be redundant with what's happening on Androlynne.