Cross the Black Canyon Bridge
This new quest will begin automatically. Cross the bridge to enter Black Canyon Mines. There's a waypoint in this location. As for the enemies, you'll be dealing mostly with the creatures you already know, like Dune Threshers, Fallen Overseers and Sand Wasps. The only difference is that in most situations there's going to be more of them than before.
Find Khasim Outpost
Your main objective is to find Khasim Outpost and sadly you can't get there simply by using the main path, because it's blocked. Check the surrounding area to locate an entrance to Stinging Winds. This is another large area that's filled by monsters you're already familiar with.
Continue moving forward. Since the new location doesn't have a main path you should consider staying close to the edges of the map. Find a proper passageway to Khasim Outpost and activate a waypoint along the way. Walk past the guards and enter the outpost.
Talk to Lieutenant Vachem
You shouldn't have problems locating Lieutenant Vachem and you must talk to him.
Enter the Command Post
The lieutenant will send you to the Command Post to consult with Captain Davyd and the entrance to the outpost is located next to him. Head down to find out that you've been trapped.
Kill the demons in the Command Post
Open the locked cage
Maghda can be found here and you'll also find out that the defenders of the city were an illusion. Get ready to defend yourself from the Copperfang Lurkers. The monsters will attack as a group and they're the biggest threat, because there's nowhere to hide. Keep running around the entire basement if necessary, decreasing the chances of their attacks. Once all the monsters have been killed open the cages to release the prisoners.
Kill the disguised demons in Khasim Outpost
Go back outside to witness a battle taking place. Help your allies in getting rid of a new group of Copperfang Lurkers.
Talk to Captain Davyd in Khasim Outpost
The last thing you need to do is to talk to Captain Davyd - he can be found in the same place where you've previously met Lieutenant Vachem. The quest will come to an end.