The Sinister Spire describes an underdark city the the necromancers tower that is in it. The adventure is the second part of the 3 part series though it can easily be played on its own.
The Adventure covers getting to the underark city of pedestal, The city its self, an island of luminescent fungus, and the Spire its self.
This adventure can also be used just for the underdark city.
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