Necromancer's Bane can be played as a direct sequel to [The Curse of Harken Hall] but is easily played as a stand alone adventure with at least 20 hours dungeoning to be had.
The valley of Highcliff Gard has had a tradition of buring its dead in the south caverns. But guards have heard disquieting noises behind the catacomb doors of late. It may be a triffling matter though another group of gaurd have not returned from their investigations.
It's up to the party to find out what is making all this noise!