Necrotus the Nihile was the former king of Quaint. He was petty, vicious, and corrupt and extended his life through alchemical means. When Necrotus died suddenly, his brother Macrotus succeeded him. Macrotus had his brother's unhealthy body hung from the walls of the city.
Necrotus had no heirs but plenty of bastard children.
The necromancers Bauchelain and Korbal Broach revived Necrotus' corpse as part of their scheme to bring down King Macrotus. They informed Necrotus that his brother had poisoned him and pledged to reinstate the old king in return for his aid. The spell Korbal Broach used to revive all of the city's dead caused Necrotus to dance uncontrollably causing him some embarrassment as he entered the city.
Necrotus' body, already damaged by decay and animal activity, began to fall apart as he danced through Quaint's streets. He had to carry his left arm after it fell off. His march to the Grand Temple was interrupted by the appearance of Hood's minion, who attempted to bring Necrotus back through the gates of death. Necrotus sent him away with hurt feelings just before losing his right arm and then his head. Bauchelain retrieved the head and kept it in a soundproof glass case among his possessions.
"Nihile" can be translated from the Latin nihile as "nothing". Including "Nihile" with "Necrotus" may or may not have been intentional on the part of the author, Steven Erikson. "Necro-", being the Greek prefix meaning death, may well have been intentional.