Go to the worg pens kill all, saving Halsin, then walk back through the door and over the ladder, kill the 2 goblins and eye then over the "bridge" and kill Minthara. Walk to where Gut is in the front hall and kill all these, then take the ramp back up to Dror and kill them.
Have some heal potions and initiate under stealth if you can. It's not difficult.
Now you have access to Underdark but do long rest and come back and kill all the goblins outside. Long rest and walk back in the front door and there are 5 in the entrance hall. Go to the west side, make the small jump and unlock the door, kill the ogre and do the puzzle to unlock the Underdark.
Spiders optional.
