Seishin Kei

Seishin Kei is an advanced technique created by the Megami Raiden Higurashi. It's combat involves her using her mind to create various forms of attack, defense, as well as illusionary abilities. After Raiden created this advanced, powerful fighting style, she was made the Kamui of Seishin Kei for being the Legendary Seishin Kei Grandmaster. Only Raiden is able to perform Seishin Kei.

Overview
The exact point when Raiden created Seishin Kei is unknown, as she's never actaully seen undergoing the exact process, (except for very few, brief, vauge flashbacks), but she claims that it was sometime after she became the 10th Division's Captain and before she defected from the Soul Society, during many of her private, secret training courses that she always underwent. What makes Seishin Kei is unique is how different it is in comparison to the other forms of Shinigami combat--three of them for actual combat, and one of them mainly for speed. Hakuda undergoes physical combat, Zanjutsu undergoes swordplay combat, Kido undergoes combat with magical spells, and Hoho is mainlly related to speed techniques, but does have combat techniques to it, (such as Senka). However, the whole Seishin Kei has to do with the combat of the mind. According to Raiden, Seishin Kei can allow the practitioner to perform tekelenisis, mind control, hypnosis, illusions, mind reading, Clairvoyance, (even if one of them can't perform Seishin Kei), among other things--and overwhelmingly skilled practitioners can perform many, if not all, of these techniques at once or in rapid succession. Once a Shinigami reaches the absolute pinnacle of this technique then they can even combine the other four Shinigami arts with Seishin Kei for an even greater fighting style yet.