“Tantra Ki Rahasyamayi – Kaali Kitab” is a comprehensive Hindi text exploring the mystical and occult dimensions of Tantra and Goddess Kali worship, blending ancient practices with spiritual insights. Authored (or attributed) to Baba Audhar Nath, the book delves into powerful mantras, tantric rituals, Yantras, and spiritual techniques connected with Shakti (divine feminine energy). It presents secret knowledge and tantric processes for sadhana, mantra siddhi, and the worship of Kali with explanations drawn from traditional sources. The work is structured across multiple sections and spans hundreds of pages, indicating its detailed approach to rituals, symbolic interpretations, and devotional practices. Published by Randhir Prakashan in India, it appeals to readers interested in Hindu tantra, Shakti Upasana, and esoteric spirituality rooted in the Shaktism tradition.