From the introduction:
Though he has lain dormant in his own crypt for almost a thousand years, continually being fed through the dipping of his phylactery in the blood of his cult of worshippers, the lich Bes-Amat has felt the growing unbalancing of the world beyond and is slowly starting to awake, ready to return and take his place within it again. The full blood sacrifice deaths of a half-dozen cultists, The Chosen, who willingly offer themselves to him is all it will take to allow him to fully rise from his slumber and return once more to the world. Returned, he will continue the reign of terror he undertook before being turned back by the first King of the Kingdom of Torranskell.
The High Priests of the lich-godling have gathered his true phylactery and The Chosen in The Blooding Hall under the False Temple of Bes-Amat and are about to start the ceremony to return him. When Bes-Amat awakens, they will willingly allow themselves to be slaughtered so that he may feed and then return to the world above. May whatever true gods still exist have mercy on our souls and send some heroes to save us all...