I didn't see this mentioned anywhere on the board, so here it is!
In order to access this sidequest, you must first defeat Magdalena Leganov and get Luciana back. After that, return to the "graveyard" area. Now that you have Luciana back, go through the left gate to get to yet another weird-ass trip.
Go into the cart to the right of the entrance to get to the hidden area. Follow the path and talk to the skeleton, Frank. Choose to "stay", and you will be teleported to a different area. Follow the path to the south, and you will come across a Tortured Soul. Slightly to the south is a Wandering Soul. Continue east, and you will see a path going north. Take that path, and when you see two iron maidens in a remote corner, search for a secret path to the left that leads up to a chest containing a Necroleech. An iron maiden to the southeast contains a Bull Skull.
To the northeast is Frank, along with Pinhead from the Hellraiser films. Talk to Pinhead, and choose "Sacrifice". Then choose "Magdalena". You manage to escape from the clutches of Hell, and Luciana gets a bonus of MND +5, and you also get a +200 XP quest bonus, but sadly, Frank is seemingly dragged into the depths of Hell, as you cannot go back for him. Why Luciana didn't teleport Frank with them was never revealed. Anyway, the exit to this bizarre place is the bell-like thing near the spinning woman.