Quote Originally Posted by Zulkhan View Post
Mehrunes remembered it right. Annhylde alone died to ress Sylvanas the first time. Which makes quite curious the necessity of 3 of them for the second ress.

Included the one killed in Andhoral, Sylvanas should have 4 Val'kyrs left. But given how the number of sacrificed Val'kyrs increased with each ress, they could not be enough to resurrect Sylvanas a third time.
Anhylde was the leader of the nine though, it is quite possible it just depends on their individual Powerlvl.