Alim asks you to kill 15 Coin Guards, then 15 Truth Guards. Once the guards have been killed, you must bring a group and enter the Blades' arena (-109,177,-37) in Maj'Dul and defeat 10 groups of heroic mobs. These fights are timed, so if you don't kill a group quick enough, the next will simply spawn on top of you.
After defeating enough enemies in the arena and getting the quest update, more will still spawn, but you can leave them and zone out.
Return to Alim and get your new title.