Omkareshwara Ji in Khandwa
Omkareshwara Ji in Kashi
Lord Brahma performed severe penance for many years and a mighty or very strong force erupted from below, penetrating the ground, radiating divine light. It took the form of a divine linga and Lord Brahma saw a divine energy that was representative of all the Vedas (Rig, Yajur and Sama Vedas), the energy that represented Akara, Ukara and Makara.
Lord Brahma saw in that divine light, the energy of Om that governs the entire universe. Lord Brahma conceived a creature with four horns, seven hands, two heads. The Lord also saw a divine energy comprising all the Vedas, Puranas, the five Brahmans (Akara, Ukara, Makara, Nada and Bindu).
Lord Brahma was so mesmerized by the Panchakshara Linga (Panch+Akshara means five syllables inscribed within the top banks) that he started singing praises to Lord Shiva, who he could see standing in front of him. The Kashi Khand describes in detail the praise and eulogy performed by Lord Brahma in the worship of Lord Shiva.
Very pleased with Lord Brahma's prayer, Lord Shiva granted the former a divine boon. Lord Brahma desired that Lord Shiva should always be present in the Shiva Linga manifested as a divine energy and the name of the Linga should be Omkareshwar.