What does the Puranas say about the birth of Mahisasura who was killed by the Mahalakshmi (Mother Goddess)?
The story of birth of Mahishasura is mentioned in Devi Bhagavat Purana: Book 5: Chapter 2. Same question is asked by King Janmejaya to Vyasa-deva.
- The king said :-- “O Bhagavân! Whose son was this powerful Mahisâsura; how his birth took place? and why, too, did he get a body of a buffalo?”
Then Vyasa told him the story of birth of Mahishasura. According to this, Rambha and Karambha were two asura brothers. They got no issues so they started a penance. Rambha submerged his body in water and then started the penance but Lord Indra in form of crocodile killed him. After that Karambha wanted to cut his head and offer to Agni but he was stopped by Agni and get a boon of very powerful son.
27-31. Vyâsa said :-- O king! Hearing thus the sweet words of Fire, Rambha quitted the hold of his hairs and said :-- O Lord of the Devas! If thou art pleased, grant my desired boon that a son be born unto me, who will destroy the forces of my enemy and who will conquer the three worlds. And that son be invincible in every way by the Devas, Dânavas and men, very powerful, assuming forms at will, and respected by all. The Fire said :-- O highly Fortunate! You will get your son, as you desire; therefore desist now from your attempting suicide. O highly fortunate Rambha! With any female of whichever species, you will co-habit, you will get a son, more powerful than you; there is no doubt in this.
After that Rambha went to beautiful place with Yakshas where he saw a Buffalo and he wanted to co-habit with her. And he does so. After that for the protection of the Buffalo he took her to Patala loka. But one day that another Buffalo came there and wanted to co-habit with her but Rambha attacked that Buffalo and in return that Buffalo also attacked Rambha in return and Rambha died. Later that Buffalo was killed by Yakshas. Yakshas wanted to cremate Rambha but that she-buffalo also wanted to burn her body with him as she was the wife of Rambha. Yakshas resisted but she ran and jumped into fire. When her body burnt the powerful Mahisha rose from that fire. Rambha also rose from that by the name of Raktabija.
The she-buffalo, seeing her husband laid in the funeral pyre, expressed her desire to enter also into that fire. The Yaksas resisted; but that chaste wife quickly entered into the burning fire along with her husband. When the she-buffalo died, the powerful Mahisa rose from his mother's womb from the midst of the funeral pyre; Rambha, too, emerged from the fire in another form out of his affection towards his son. Rambha was known as Raktavîja after he had changed his form. His son was thus born as a very powerful Dânava and became famous by the name of Mahisa.