Priests of Holy Grail is a powerful Reiki system for psychic protection and exorcism by Ömer Volkan Akkuş. The system uses Catholic symbols to banish negative entities - but you do not need to be Catholic to utilize the system (see note below). The examples in the manual deal with demonic possession but this energy can also be used for more "everyday" cases of psychic attacks. Upon receiving the attunement, you might experience a wall of protection around you by the priests themselves.
Note: Some people who work with Reiki have issues with the Catholic Church (as do some Protestant Christians!) - please do not let that get in the way of using this system. The Catholic Church for over 1,000 years was the predominant spiritual path for people in the West and many great mystics of yore were Catholic, including female saints.
The manual is provided in PDF format. Please note: English is not the native language of the manual writer.