Nels comes from a small village in Skyrim. One day, his village was attacked and his daughter, Olga, was killed. He blames the Imperial Legion for her death because they did nothing to stop the attack.
A client has arranged a party in order to kill off some enemies with the Dark Brotherhood's help. The goal is to kill all the guests, and a bonus is given if nobody witnesses any murder.
When the Hero first enters the building and head upstairs, they will see Nels and Neville, a former member of the legion, having a conversion about what they plan on doing with the money. This conversation will soon become heated and they will go their separate ways.
If the Hero speaks to Nels he will state he feels slightly protective of Dovesi Dran because she reminds him of his late daughter. If Dovesi is killed before Nels is, he will say its like watching his daughter die all over again.
If Nels is one of the last two guest to be murdered, and the other is either Neville or Primo Antonius, he will think they're the killer and attack them. If Dovesi and Nels are the last two guests, and both trust the player, Nels will assume the killer is coming through the window.
Despite the fact that most of the guests see him as nothing more than a drunk, he is the only guest to conclude that somebody was hired to kill them.