There are 4 paths to the Underdark
1. Under the goblin camp
2. Through Auntie Ethel's fireplace and a well hidden wooden face door
3. Feather fall + jumping down the big dark hole at the end of the Blighted Village's well area
4. The Zhent hideout has an elevator to it through an illusion wall
So evil characters can get down there as well through one of the other paths.
