From publisher blurb:
In Challenge of the Ashen One, the heroes meet an ambitious thief named Lyanna who recently came into possession of teleportation runes to reach the Bloodfall Shaft. Many adventurers know of this fabled dungeon said to be guarded by a dangerous mage. It can only be accessed by teleportation magic when the dungeon's overlord issues a call to valiant folks to come. Lyanna wants to share the treasure with the characters but she seeks to keep a magic dagger that, legend has it, is hidden in the dungeon. She says the magic item is the Bloodletter's Knife.
The characters teleport into the Bloodfall Shaft and soon discover they are not the only adventurers trying to delve into this extraplanar compound. A despicable mage named Barraster Jinnock and a group of mercenaries thwart the characters' attempts at exploring the dungeon's different levels. Ultimately, the characters must overcome these enemies or make a truce with them to finally confront the Ashen One. The strange undead being awaits whoever survives or outwits his traps and guardians at the dungeon's fourth level. It is a tough battle to the death.