Shiva is called Bhairava in the Kashmiri Shiva tradition. Shakti, when it inwardizes, is Shiva. Ravanath means to absorb all existence back into pure awareness. This appears fades away into awareness itself. So this is Bhairana, just all of this is contained in the one letter, Bhairava. It's a crucial idea, transcendent, eminent God.
On the auspicious occasion of Durga Puja, Swami Sarvapriyananda speaks on the significance of the Divine Mother.