From publisher blurb:
Trial of the Underkeep is a Dungeons & Dragons adventure optimized for 4th edition. Some things are better left buried and entombed, like an entire castle that slid into the earth 1000 years ago, hiding its shameful secrets. It was only a matter of time until it its doors were blundered upon and unsealed, unleashing unimaginable horrors upon a small town. What unknown abominations stir in the slimy subterranean castle? Something has punctured through from another plane of existence. It has tasted your world and found it easy to digest. Worst of all now you have been afflicted by its presence and you must save yourself as well. Can anyone survive the Trial of the Underkeep? 19 New Creatures 26 New, unique Artifacts and Treasures, some that are as dangerous as the Monsters!