Bassilus the Murderer, also known as Retrieving Bassilus' Symbol, is a side quest in Baldur's Gate. You will likely hear of this quest first from rumors gathered in Beregost, although you receive the quest from Kelddath Ormlyr in the Temple area. Bassilus himself is in the Red Canyons area south of High Hedge. Once you have arrived in the Temple area, enter the Song of the Morning Temple and talk to Kelddath Ormlyr. Give him Bassilus' Holy Symbol and in return you will receive 1000 xp and 5000 gp.