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.
Lord Shiva accordingly gave permission and said that the Shiva Linga was to be called Shiva Panchayatan, symbolizing Akara, Ukara, Makara, Nada and Bindu.A devotee who takes a holy dip in the Matsyodari shrine and worships Omkareshwar will have no fear of rebirth.
The person who worships Omkareshwar gets the benefits of performing Ashwamedha Yagya. Worshiping Omkareshwar is equivalent to chanting one lakh Rudras and is equivalent to worshiping all the Shiva Lingas in the world. A person who is a devotee of Omkareshwar, even if he dies at a place other than Kashi, will attain salvation.
Lord Shiva told Lord Brahma that with the radiating energy of Omkareshwar, Lord Brahma would be successful in his task of creating man. After giving all the boons to Lord Brahma, Lord Shiva disappeared inside the Linga.Earlier there were five Shiva Lingas representing the Shiva Panchayatan. Akareshwar, Omkareshwar, Makareshwar, Nadeshwar and Bindu Linga.
Now only three lingas are left, Akareshwar, Omkareshwar and Makareshwar. Omkareshwar Linga is also known as Kapileshwar and Nadeshwar. The Omkareshwar Linga was said to be on the banks of the Matsyodari Tirtha, where the river Ganges overflowing in the rainy season was also found.
On the day of Ashtami and Chaturdashi, by taking a bath at Matsyodari shrine and praying to Lord Omkareshwar, the devotee is absolved of all sins. One who prays at Lord Omkareshwar temple is really lucky and gets a place in heaven. Their forefathers were overwhelmed with ecstasy on seeing their descendants praying in the above mentioned temple.