The Sunken Village of Little Corth

From the publishers blurb:

'The Sunken Village of Little Corth' is a 2nd level Dungeons and Dragons adventure centred on a time-paradox puzzle. The PCs travel across a necrotic marsh (the Grey Creeping) to a sunken village where, upon being transported back 2000 years into the past, they must prevent a necromancer freeing Orcus (demon prince of Undeath) from the imprisoning veils of the spirit plane. If only it was as simple as that, for the PCs must also contend with deactivating a giant mechanical orrery, and be sharp enough to realise that the useful items that helped them survive the Grey Creeoing must be found and placed for their 'future-past' selves.