Mahishasura is regarded as an asura according to the Hindu mythology. He was bestowed with a boon that none but a goddess could only defeat him. He is said to have defeated all the gods and then expelled them from heaven.

Birth of Mahisasura
As per mythological stories Danu had two sons named Rambha and Karambha. They however, did not have any sons. To be blessed with sons they began practising penance by standing in water. Karambha, while doing got carried away by Lord Indra who took the form of a crocodile. He was subsequently killed. Rambha became depressed at the death of his brother and tried to kill himself. Lord Agni then appeared in front of him and granted him the boon to have a child who would conquer the world. Rambha then came in contact with a water buffalo, Princess Shyamala who conceived a child. Once, Rambha was attacked by another buffalo demon and was killed. At the death of her husband the buffalo also wanted to end her life. When the pier was lit, Mahisasura burst out of the womb of his mother. With time he became the king of demons.

Mahisasura after gaining power began torturing the gods and expelled them from heaven. The gods then assembled together and approached Lord Brahma, Lord Vishnu and Lord Shiva and narrated them the complete incident. The gods then emanated a fiery light from within that created a female who enveloped the earth with her brilliance. The female deity was Goddess Durga. The gods then furnished her with different types of weapons. Mahisasura became very agitated when saw the goddess pervading the three worlds with her lustre. He sent his a huge army to combat her but at the end of the battle the demons were defeated. Mahisasura then summoned his courtiers for a meeting. One of them known as Vighasa advised him to propose the deity for marriage. Thus, Dundubhi, the son of Maya was sent to the goddess with the message. The later however, rejected the marriage proposal stating that she would only accept the person as her husband who would overpower her and shatter her pride. The messenger the returned back and narrated the incident to the demon king.

Battle between Durga and Mahisasura
Mahisasura upon hearing the clause began his preparations for a battle with the goddess. At his command a vast and the invincible demon army was organized. The army was fully equipped with the varied types of arms and ammunition. A fierce battle then took place between the demons and goddess Durga. However, the demon army could not withstand the power of the deity and eventually all died. After his entire army was destroyed, Mahisasura came in direct conflict with the goddess. In his buffalo form he laid low and attacked the goddess. A fierce battle waged between the two where ultimately Mahisasura was killed by the goddess.