While Gehenna's theme is BDSM (consensual suffering), Purgatory's theme is torture (non-consensual suffering). The path of Purgatory is filled with continuous pain.

In Purgatory, the rocks in the rooms have a high chance of being replaced by spiked rocks. There is also a new type of obstacle for rooms, an urn of ashes that projects a circular area of fear that prevents Isaac from shooting (similar to the Cursed Death's Head, but fixed to the ground and does not disappear when the room is cleared).

The color of the floor is blue-gray and the enemies thematic would be ghosts, specters and souls in pain.