Board Thread:Warhammer 40k General Discussion/@comment-108.23.49.87-20130605000245/@comment-7186329-20130613171041

Again with the internet...

Isha would need a lot of power to heal the body of The Emperor in the first place. Not to mention how weakened she would be after escaping from Nurgle. Considering that the Eldar Rhana Dandra prophecy only mentions a single Eldar god surviving, it is likely Isha will die after using all her power to heal the body of The Emperor. And even when she does there is no way to completely restore/preserve His power.

And it is not only a question of Sanity. What about the character of the emperor, or His knowledge? If his mind was diminishing, then how much precious wisdom and knowledge has He lost? There is no way to restore that, provided it some would even be missing in the first place.