Opened in 2086, the clinic was an elite private hospital when its director, neurosurgeon Matthieu Zweidler, was chosen to become the proxy of vitakinesis. Zweidler used the clinic and its network of affliated hospitals to quietly build his order until the Psi Orders collectively revealed themselves in 2106. Montressor remained the primary training facility for A/O, and became one of the solar system's most famous, and most effective, healthcare facilities.
By 2120, the clinic had essentially become its own small city, subsuming the suburb of Mattenz in practice if not in law. Five additional buildings had joined the original 10th-century monastery to comprise the clinc's campus. In addition to the Aesculapian Order's administrative offices, the complex is a fully functioning hospital with an emergency ward, outpatient facilities and a Free Clinic serving those unable to afford top-notch care. The Organ Bank occupies its own building, as do classrooms and a dormitory for trainee vitakinetics. Belowground, these buildings are connected by a maze of steam tunnels nicknamed "Knossos" by the staff.
Montressor Clinic is the seat of the order's orthodox "rationalist" approach to vitakinesis, as opposed to the secondary training site in Port-au-Prince, Haiti. Tension between vitakinetics trained at Montressor and those trained in Haiti are common, with the Montressor faction having the fairly explicit support of Proxy Zweidler.
The clinc's regular security staff is overseen by a former Special Forces officer named Jakob Neihaus, and is staffed almost exclusively by neutrals. Montressor is also the headquarters of the Black Company, an elite corps of psion soldiers who report directly to Zweidler himself.
A soap opera called Montressor! is popular across the solar system; set at the clinic, it dramatizes the lives of psions for mass entertainment (and to promote a positive image of them in the general population).
The clinic was named after Zweidler's mentor, but many characters in the Trinity Universe associate it with the narrator of Edgar Allen Poe's story "The Cask of Amontillado." The line "My god, Montressor!" is quoted by multiple people.