Grimgnaw is a dwarven monk and member of the Long Death, an evil monastic order which worships the very essence of death, which is personified as the "Silent Lord", and seeks to bring as many living beings to death as possible. He was originally from the clan of Bruenor Battlehammer, the king of Mithril Hall, but left to pursue initiation into the order of the Long Death. Akin to the cult, Grimgnaw has a deep, morbid fascination with death and dying and detests undead, as he believes undeath to be a means of escaping a natural death. In the original campaign, Grimgnaw is one of several henchman who can be hired by the main character.
Source: Wikipedia, "List of Neverwinter Nights characters", available under the CC-BY-SA License.