Lair of Infinite Agony is a new zone in Tiny Tina's Assault on Dragon Keep DLC
You will find a good horde Skeletons waiting for you in here.
Accessing Next Area
Head forward and over to the West to make it into the next area. it is very close to where the Skeletons like to patrol so keep an eye out for them if you want to avoid them. Head over to the South and open the door there to press on forward. Go around the wall, destroying the various Skeletons that appear in front of you and go over to the lift in the middle. Ride it on up to get to the top and head out the corridor to get to the Hall of the Dead