Jambavati was unhappy when she realized that only she had not borne any children to Krishna while all other wives were blessed with many children. She approached Krishna to find a solution and to be blessed with a son like the handsome Pradyumna, Krishna’s first-born son from his chief wife Rukmini. Then Krishna went to the hermitage of the sage Upamanyu in the Himalayas and as advised by the sage, he started to pray to the god Shiva. He did penance for six months in various postures; once holding a skull and a rod, then standing on one leg only in the next month and surviving on water only, during the third month he did penance standing on his toes and living on air only. Pleased with the austerities, Shiva finally appeared before Krishna as Samba (Ardhanarishvara), the half-female, half-male form of the god, asked him to ask a boon. Krishna then sought a son from Jambavati, which was granted. A son was born soon thereafter who was named as Samba, the form Shiva had appeared before Krishna.
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Krishna wanted his son to be exactly like Shiva. Shiva’s main function is to destroy creation. For his son to be like Shiva meant that the boy would be the cause of the destruction of his entire race. This was what Krishna precisely wanted because the Yadus could not be defeated by anybody. Immortality for humans is out of question therefore at the end of the Yuga the Yadus would destroy each other. Later Samba played an instrumental role in this.
Mayasura was a great ancient king of the asura, daitya and raksasa races. Mayasura had befriended a snake named Takshaka and lived with him in the area of Khandavprastha along with his family and friends. But when the Pandavas came there after the partition of Hastinapur, Arjun burnt the entire forest, forcing Takshaka to flee away and killing everyone in the forest. Along with his family. So, Mayasura decided to surrender to the Pandavas. Krishna was ready to forgive him and for this act, Mayasura built a very grand palace named Maya-Mahal, where the Pandavas would perform the Rajsuya Yagna. He also offer him the gifts like, a archery,a sword and many more. He built his capital and called it Maya Rashtra.
Upamanyu is a Rigvedic rishi. He is said to be the father or ancestor of sage Kamboja Aupamanyava referred to in the Vamsa Brahmana of the Sama Veda. Once Krishna went to him to take advice as Jambavati (Krishna’s wife) wanted a son like Pradyumna. On his advice Krishna starts to pray to the god Shiva. After many months, Shiva finally appears before Krishna. Krishna then soughts a son from Jambavati, which was granted by Shiva.
After slaying Kansa, Krishna visits Kubja with Uddhava as promised. Kubja worships Krishna with her companions and offers him a seat of honour. As Kubja readied herself for Krishna, Krishna made himself comfortable with Kubja fulfilling his promise. By embracing him, Kubja’s desire is fulfilled. She requests Krishna to stay with her for some time, however Krishna left for Uddhava’s residence, promising he will fulfil her desires again.