Changing of the Guard - Blades  

This quest is initiated by clicking the chest of ceremonial daggers in the first room of the Court of the Blades.

To complete this quset you must kill either a Truth or a Coin tower captain. These spawn at the top of the capturable towers in Maj'Dul. Each tower can be controlled by one faction at a time, which allows places that factions guards in the immediate area. The captains are located at the very top of the towers.