Elsa was a barmaid at the Stonehill Inn in Phandalin.
While The Party was investigating the Redbrand Bandits, a group of their thugs ambushed the party at the Inn and took Elsa hostage. The ensuing fight caused the Redbrands to murder Elsa.
Ialtóg Ulchabhán in particular felt responsible for the death of Elsa. He tried to have her revived in Neverwinter, but the attempt failed.