Ossuary

"After the Night of the Bloody Riots, the guards decided to condemn a whole wing of the prison so they could dump the bodies in there."

The Ossuary is a third level biome.

There's a point where even mass graves won't work to fit all the bodies. No, after the night of the bloody riots, they knew that they could not afford to dig massive holes. Instead, an entire section of the prison was decided to be the perfect place to host them. Then it was set ablaze, and the ashes spurted out. Bones and flesh now litter the floor, and bodies that are barely even recognizable as human litter the grounds. However, with so many bodies, even fire was not fast enough. Before it all could be burnt down, the bodies began to awaken, and the flesh started to move.

A Slasher elite can be found here who drops the Ram's rune. He disappears after being defeated once.

Loading Screen Quotes

 * "After the Night of the Bloody Riots, the guards decided to condemn a whole wing of the prison so they could dump the bodies in there."
 * "A thick layer of ashes covered the walls of the place. Filth crept into every nook and cranny."
 * "One of the worst places on the island... Or one of the safest, depending on who you ask."

Access
A Spider Rune is required to access this biome through Promenade of the Condemned and reaching Prison Depths. Also, this last one can be skipped by using the passage with the Teleportation Rune from Promenade of the Condemned.