The Demon Narakasura fell in love with Goddess Kamakhya once and he wanted to marry her. But as a Goddess cannot marry a Demon or Asura, Goddess Kamakhya played a trick to save herself. She laid a condition that she would marry him only if he builds a temple for her within one night. Narakasura agreed to it and almost finished building the temple overnight. This scared Goddess Kamakhya and before the final steps of the temple were completed, a cock was sent to announce the arrival of dawn by crowing, very much before the due time for the birth of dawn. Angered by the crowing of the cock, Narakasura killed the cock on that spot. But according to the condition Narakasura couldn't marry Goddess Kamakhya after that. It is said that the present Kamakhya temple is the same that Narakasura had constructed for the Goddess.
One more Legend…
The evolution of Yoni in Kamakhya Temple has its origins in the mists of unknown history and antiquity. The Kalika Purana refers a dialogue between Devi and Shiva, where Devi asks Shiva about the yoni worship and the legend of Kamakhya. Shiva replies to her questions with a short explanation on the origins of Kamakhya.
According to hallowed tradition, Lord Brahma after having created the Universe, prided himself on his great accomplishment as a shining symbol of the supreme force of primordial creation. The Supreme Goddess was put off by the overweening arrogance of Lord Brahma. In order to suppress the pride of Lord Brahma, SHE created a demon out of herself and named him Kesi. Kesi chased Lord Brahma around the four corners of the universe, with his mouth wide open and ready to swallow Lord Brahma. Lord Brahma fled and absconded from the universe. Kesi then built a city named Kesi Puri from which the ever reverberant sounds of “Brahma Kunjah” (Kill Brahma) came out. Lord Brahma, realising his original mistake, retraced his steps and after giving up his vain pride, offered his fervent prayers to Mahashakthi in these words “Divine Mother, I am a fool to have deluded myself with the omnipotence of my superlative powers, particularly when YOU are indeed the ORIGIN, SOURCE, BEGINNING, MIDDLE AND END OF IT ALL. Please forgive this sinner for this grievous act OF MISDEMEANOUR. I pray that YOU understand that Kesi has to be put down for the sake of the larger good of the world. Have grace on us, Oh Supreme Goddess.” Shakthi took pity on Lord Brahma and destroyed Demon Kesi with a simple blow from her mouth ending in ‘hum’ (the syllable of destruction).
In order to atone for his sins Lord Brahma had to create a mountain out of Kesi’s ashes and cover it with grass for the cattle. Accordingly Lord Brahma created a mountain. The Gods and Goddesses offered their salutations to Mahashakthi from atop the Govardhana Mountain created by Lord Brahma. Maha Sakthi pleased with their prayers burst forth as a spring from an opening atop the hill, and commanded Lord Brahma to know and understand that this place indeed would be the very Centre of Creation and the Eternal Source of his Creative Power. Devi had placed the yoni in Kamarupa essentially for the good of the world.After he was absolved of all his sins, Lord Brahma brought down a luminous ray of light from the heavens and placed it on the yoni circle.
The yoni is the quintessence of feminity and is a yantra for many Shaktha-based Tantric Cults in India. Represented as a downward pointing triangle, it stands for the sacred feminine womb, from which all life springs. The worship of the Goddes at Kamakhya is in this form of her creative power. She is venerated as a life giver. KAMAKHYA TEMPLE HAPPENS TO BE ONE OF THE VERY FEW HINDU SHRINES WHERE THE GODDESS MAHA SHAKTI IS WORSHIPPED IN HER REPRODUCTIVE ASPECT AS THE SOURCE OF ALL LIFE ON EARTH.
One more Legend…
Another tradition has it that the Kamakhya Temple was built by Kamadeva, the God of Love. According to this tradition, when Lord Shiva went into deep meditation upon Sati’s death at the yagna performed by her father Daksha, the Gods grew very worried and anxious about the uncertain future of the world. They came to the conclusion that further creation would only be possible if the divine UNION between the Holy Mother and the Divine Father is made possible once again. In order to bring about this UNION, they sent Kama to shake Lord Shiva out of his Yogic State of trance and thus make him fall for Parvathi, the daughter of Himavan who was the very reincarnation of Sati. Kama let his arrows fly from his bow. They struck Shiva and woke him up from his trance. Furious with the disturbance, Shiva burnt Kamadeva alive with a single glance. Later at the instance of all the Gods, Lord Shiva brought Kama back to life. Unfortunately, Kama lost all his charm and good looks. Lord Shiva however comforted him with these words: “Don’t worry Manmadha. It was all a part of my divine act. You will regain your good looks once you build a temple for my beloved Sati at the spot where her vagina fell.
One more legend...
Despite her husband Lord Shiva's disapproval, Sati had gone to attend the universal 'yajna' organised by her father Daksha. Shiva was not invited, and was also abused by Daksha. Unable to bear the insult, Sati committed suicide. Upon hearing the news , Shiv arrived on the scene, picked up the body and began a dance of destruction. Vishnu tried to pacify Shiva: the body was cut into 51 parts. The spots on earth where each part fell was identified as 'peetha'.
But the place where her uterus fell was not known till the god of love, Kamadeva, searched it out to rid himself of a ceratain curse of Brahma's. Kama regains his body here. The place came to be known as 'Kamarup' and the presiding deity as 'Kamakhya' or one worshipped by Kama.