Mercury the god!

http://en.wikipedia.org/wiki/Mercury_(mythology)


This Roman god was so cool that he would often prevent the last of a clan from
being killed.    That was rumored to be his thing.    You kill the last person of a
clan and Mercury come down and wipes you off the surface clean and fast.
So if you believed in such a tale you would always leave the last of your male
enemy alive and well so as to not end out fraked.