Kill Cambion under Fornost

Hired by Bishop Paul of Ra as a sign of good will, and offered 2000gp each the party are asked to investigate the old temple to Moloch and find the Demon that had been killing and kidnapping people from Fornost. The demon is believed to have been cut off from his ally Sarn Durgba when his armies escaped across the planes to the nameless hills. Cambion, Son of Succubus and servant of Moloch
The party find the ancient Dwarven citadel of Dol Goldur under Fornost Erain, and more than 1 demon, also a Royal group of Dark Elves, demon, Orcs, Trolls and Bugbears, Dol Goldur, ruins of the ancient dwarven city under Fornost
Cambion had lots of prisoners, but why - for food - or for some other dastardly plot....