The custom of these guhya or secretive Bhairava is surely an oral custom that is constant during the guru disciple tradition. Their karmakand rituals and tactics are solution, they're not composed down but only learnt and practiced in guru disciple tradition. A Kapalik with his Cranium Bhairava, in his Kapalika https://directoryholiday.com/listings13203118/considerations-to-know-about-kaal-bhairav