Demonslayer is a famed two-handed sword, its primary function as clear as its name. It was brought down to Exile in the First Expedition, wielded by Karzoth (whose name literally means "Demon-Slayer" in a debased version of Soruharva). When the First Visitation failed, Karzoth was slain by a Haakai, and Demonslayer broke into three parts. The hilt was taken by the Nepharim, the blade by the Dark Slithzerikai, and the tip by the lich Drath to his crypt in the west. After the Kingdom of Avernum was established, the three pieces were eventually found again by Hawthorne's Assassins and reforged by Boutell. It was used by adventurers to defeat Adze-Haakai and to finally banish the power of Grah-Hoth. It also figured in a prominent role in both the assault on Garzahd during the Empire-Avernum War and the assault on Rentar-Ihrno during the Vahnatai retribution.
In the first Avernum game, Efram in Silvar (Or, alternatively, his wife, Anastasia, who will tell you to speak to him about it), will tell you about the existance of this sword, and how it was taken by a group of adventurers, and that noone knows the location of this sword anymore.