An additional skull-like accessory inspired by the game's mutant enemies.
Go for the Deluxe Edition repack. The XP plug-in alone makes the second playthrough (Kasane’s route) much less tedious, and the artbook is a rare treat that retail owners often ignore.
Assuming you have acquired the from a reputable scene group (e.g., FitGirl, DODI, or ElAmigos), follow this protocol: