This level is fairly straightfoward (seems to be a theme in this game!) as are the others. There are plenty of chests in this level, so open them as youu find/see them. To beat this level, all you really need to do is to retrieve the 4 drow keys, and then, using them, unlock the door leading to the end of the level.
The enemies in this level include Hellhounds now. Hellhounds aren't very difficult to defeat, but they do have quite a bit of health and have some ranged attack spells (though those are very weak). The boss in this level doesn't say anything to you, but you can tell that it's a boss because of the difference of it from other groups of enemies. The boss is easy to defeat and should be no problem for a party that has made it this far.