Stool is also an 'entry pass' to the Myconid cavern.
A safe place to rest will probably be a welcome event, especially if you run a gritty Underdark.
If you want to make Zuggtmoy a big deal in your campaign, the PCs will have to get clues and foreshadowings about her somehow. The Myconids can do just that - the implications of what they see / hear can be awe-inspiring, after a night to mull it all over - without having an over-powerful Big Boss Fight in the process.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.