Night Lies One of the toughest fights in Act 1.

The fight can be made a whole lot easier by closing the door after you've entered the main room, as this will keep the waves out of the game until after you've dealt with "Captain" Qerth and his goons. The main problem is, however, that there are four archers in there, two of which are normal mobs, so they have a good amount of health.
Took me a few tries to get it right. I assassinated one of them right away, then I stealthed and ran for the stairs, and pulled them up to me. Followed this by a Combustion Grenade and quickly took care of the stunned archers. After this it was just a matter of evading the remaining mobs attacks, while slowly shooting them down. Took quite a while, especially considering Qerth's huge health pool (he also had two or three healing potions).

After this I could save, since the adds were still camped out by the entrance, behind the closed door, and I wasn't engaged in combat with them. There's one major problem when you start pulling the adds, which is that archers will spawn on the stairs behind you. What I did was to pull them unstealthed, and as soon as the archers spawned, I stealthed and took them out first. Then it was just a matter of pulling the remaining Guard Pretenders one or two at a time. There are two elites amongst them, so it'll take you quite a while to bring them down. I would recommend always pulling unstealthed so you have it in case you mess the pull up and pull too many.