From The Vault
This quest is essentialy the opposite of the quest 'Join the Khans. Instead of receiving an XP reward for killing the slaves, you receive an XP reward for freeing the slaves. Doing so isn't complex, but can be very difficult for low level characters. Basically, all you have to do is kill all of the Khans. If you manage to do so, and either of the two slaves survives, you can talk to them for a reward of 200 XP per slave. It is probably a good idea for lower level characters to undertake the 'Join the Khans' quest instead as this gives a guaranteed 500 XP rewards and is ten times easier, unless they are trying to maintain a good karma.
