Random themed levels packed together for one reason, to entertain! Fight your way through several areas of hell even if it's not like that you will ever leave that place.. The variety of level designs try to increase the fun factor, just like the hidden ammunitions and secret areas, look for them whenever you can.
This supposed to be the part of the BHS 1.0 version, but for some reason it became a separate release. Try to find secret stuff, stay alive, and get out of the misty graveyard. And of course have fun :)