From the back of the module:
"The Demon God...
A name so old and so obscure, most people no longer remember the terror it conceals. Now, something evil has slithered its way into the village of GOlden Lake, and into the minds and souls of the villagers. Has the old temple to the demon prince Ochremeshk become a threat again after so many centures? And how can it be stopped when its location remains lost in plain sight?"
The cultists of the demon god are out to get you. Track them down and wipe them out in tehir own lair in this challenging d20 adventure for 14th and 15th-level cahracters. Demon God's Fane serves as a companion to the popular The Book of Eldritch Might, featuring many of that sourcebook's high magic prestige classes, feats, spells, magic items, and more.
NOTE: While Demon God's Fane uses much information from The Book of Eldritch Might (Second Edition), it does include suggestions on conversion for those who do not own that book.