Night Masks

R.A. Salvatore's The Cleric Quintet tells the tale of the scholar-priest Cadderly, who is plucked from the halls of the Edificant Library to fulfill a heroic quest across the land of Faerûn.
The assassins of the Night Masks stalk the shadowy streets of the city of Carradoon, led by the sinister killer known as Ghost. Cadderly struggles against the dreaded Chaos Curse in these dark, evil-haunted alleyways, with a silent death around every corner.
From the Paperback edition.
Night Masks follows an eccentric young scholar-priest as he fends off the hordes of Castle Trinity to save his home, friends, and his own life. Besieged by the Night Masks--resident assassins--he must uncover the killers' latest activities and put a stop to them.