Originally Posted by jmos
There are 4 entrances to the underdark I can think of (and I feel like I'm missing some):[/spoiler]

[quote=jmos]2 - Teleport from Auntie Ethel's cave. Although I have yet to be able to get through that door, it seems bugged.

That one is easy. Do not click "on" the door, just scroll the camera through it and click on the other side when wearing Ethels mask.
Do not equip Ethels Mask if she is still alive.
But you knew that already. ; )

Originally Posted by jmos
3 - There is an elevator from the Zhent hideout. This gives you much better positioning on the hard encounter you drop into from option 1.

WHAT!?
You serious? Where?
Gotta do research fast.
Where the hell!? I was in there 3 times and I did not found it. WHERE. A juicy new discovery! ^_^