A Bonethief is a skeletal creature that is able to wear the skins of people in order to appear human. At a glance, possessed humans appear normal, but they quickly move to attack the player. When the human host is too damaged, the Bonethief will burst from the body, having a very negative effect on the player character's sanity. In some cases, the bonethief will burst out of their host willingly, as evidenced by the monk at the end of Chapter 3, where the bonethief emerged from the monk upon the declaration of his Ancient's name despite having no sign of injury at all. They are vulnerable at the neck, and once exposed may be quickly dispatched by targeting the head. If given the opportunity, they will attempt to possess the player, meaning instant death if not shaken off in time. In some cases they possess zombies. Bonethieves are also nimble enough to dodge projectiles, but can be shot when winding up for possessing someone, in the process of doing so, or when using a standard attack. Oddly enough, Bonethieves cannot dodge crossbow bolts, even though they are capable of dodging Chakrams, bullets, and even the spread fired by a shotgun.
Like most creatures, Bonethieves vary based on alignment.
Chattur'gha Bonethieves are a bit stronger and more resilient than the others. They are more muscular, and have longer claws. Chattur'gha's bonethieves are also more aggressive and attack faster than other alignments. If their head is severed, they will instanly crumble and be vulnerable to a finishing move.
Xel'lotath Bonethieves lack heads, the usual weakpoint, having only green, flying spheres in place, making them harder to kill. Steal sanity upon successful attack.
Ulyaoth Bonethieves are crystalline in appearance and drain magick with each attack. Like Chattur'gha's ones, their heads can be severed.