From Creatures Wikia
These Norns look sweet at birth, but in adolescence... If cornered then they can react dangerously. The males are particularly nasty. The females initiate mating (males do in normal Norns). Winning duels gives these Norns a boost in life force. A small cocktail of sleeping pills and pain killers (both injections from the Science Kit) will help soothe frustrated Night Norns.