What is karna guru and Is it compulsory to take mantra from karna guru?
Robert Svoboda, quoting Vimalananda (his Aghori mentor):
Vitthala wanted to initiate him into the undifferentiated reality, by killing, butchering, and cooking: Sadguru, Karnaguru, and Upaguru. Have you ever heard of the Sadguru, Karnaguru, and Upaguru? The Sadguru kills the aspirant - separating him from his mundane existence. The Karnaguru flays the carcass: the ego. All the accretions of untold births, the false personality, is chopped into tiny pieces. When my Mahapurusha cut Haranath Thakur, my parents' guru, into tiny pieces and removed Sattva, Rajas, and Tamas from the pile of sixty-four, this is what He was doing. The Upaguru cooks the ego in the fire of Shakti, and the result is a tasty dish: an enlightened being. The best guru, of course, combines the Sadguru, Karnaguru, and Upaguru into one, like my Mahapurusha.