Kill Venril Sathir and harvest the harp to the right when you enter the throne room.
Kill The Leviathan and harvest the harp under one of the tentacles on the right hand side as you enter the room. ( -25, -24, -110 ) Copy/waypoint -25, -24, -110
Kill Druushk and harvest the harp in the room he spawns in. ( 1672, -364, 254 ) Copy/waypoint 1672, -364, 254