This is The Shattered Gates of Slaughtergarde published by Wizards of the Coast. It is a D&D v3.5 game set in the Valley of Obelisks, a new setting for this scenario.
I've set the valley location in Greyhawk. It is located in the northwestern Lortmill Mountains, east of Gran March and north of the Duchy of Ulek. A river, the Marrilach, runs through the valley to the southwest as a tributary to join the Lort River.
This is a short-term, low-level campaign. Characters should advance from first through about seventh level. If there is interest in continuing I may add the updated White Plume Mountain and
Tomb of Horrors scenarios which would extend the campaign to tenth level.The characters are all locals of the Valley of Obelisks. The valley is a huge place which is home to many races and classes. The valley is a temperate, agricultural frontier located far enough from the governing centers of Gran March and the Duchy to be insignificant.
While adventuring, the group discovers an evil plot in motion. This is a combat intensive campaign with a small bit of role play. Most of the action takes place in dungeon crawls.