Introduction
Shambara is an Asura, feared for his skill in sorcery and illusion, who abducted the infant Pradyumna, the son of Krishna and Rukmini, and was killed by him years later when he had grown into a young man.
The abduction
A prophecy said that Pradyumna, Krishna's son, would kill Shambara. To prevent this, Shambara stole the infant soon after birth and threw him into the sea, where he was swallowed by a large fish. The fish was later caught and brought to Shambara's own kitchen, and his wife, or in some accounts his cook, Mayavati, found the living child inside it and raised him without her husband's knowledge.
Mayavati and Rati
In the fuller Puranic version, Mayavati is Rati, the wife of Kama (the god of love, reborn as Pradyumna), living in Shambara's house under this name after Kama's death, and waiting for her husband's return in this new form. The sage Narada eventually told her the truth. She taught Pradyumna the arts of illusion (maya), so that he could face his enemy on equal terms.
Death
When he was grown, Pradyumna challenged and killed Shambara, and then returned with Mayavati to Dwaraka, where the family recognised him as the lost son.