Nightfall
Sage of the Scarred Lands
*decides to give your PCs some helpful advice*
Also consider the fact they might have to actually gather ALL the parts of the Rod of Seven Parts or even find/get the Crook of Rao to help banish Kyuss and his minions back. While I can understand Midnight in Greyhawk, there's still some time left before Kyuss ascends the panetheon. Plus there's always the chance Vecna might object to being treated this way.
Also consider the fact they might have to actually gather ALL the parts of the Rod of Seven Parts or even find/get the Crook of Rao to help banish Kyuss and his minions back. While I can understand Midnight in Greyhawk, there's still some time left before Kyuss ascends the panetheon. Plus there's always the chance Vecna might object to being treated this way.