"Do you really wish to know?" — Spoilers from the books and/or adaptations to follow!
Adalbert was a crossbowman of the City Guard who fought in the ranks of the Order of the Flaming Rose.
He participated in fierce battles to take control of the Trade Quarter, resulting in the Order winning a Pyrrhic victory. A seriously wounded Adalbert went with his remaining strength to the Cloister of the Flaming Rose in the Temple Quarter. Being in a state of agony, he informed Jacques de Aldersberg what happened, and then told the Master about the death of Roderick de Wett caused by Geralt. The Grand Master then thanked the soldier for his faithful service, just before Adalbert died from his wounds.