The Bliss of Sacrifice
Somewhere, far away from the main city of R., there is a temple that appears almost completely ruined, however, somewhere beneath the ground there exists a very strange sect of monks.
The monks serve as vessels for a mysterious knowledge and therefore dedicate their life entirely to practices that make them almost completely immune to pain, as they are the keepers of certain great secrets and that knowledge must not be revealed, even if the monk is captured by the foes. Because of the constant pushing beyond the limits of the body, the monks develop a very high threshold for pain.
Through their spiritual practice they also learn to detach their soul and consciousness from the physical body in case of an overly extreme situation, which makes their mind absolutely invincible.