Krishna needed a son with destructive power, so he asked Shiva for a son who was like Shiva. Samba is also a name of Shiva.
Samba is the one who brought about the end of the Yadava clan. He disguised himself as a pregnant woman and his friends asked a few sages if they could tell if the child was going to be a girl or a boy. One of them said, ‚This boy is going to give birth to an iron club. It will be the instrument with which the Yadavas, including Krishna and Balarama, will be destroyed.
Read about Samba here