 The Mahabharata tells the story of Manasa 's marriage . Sage Jagatkāru practiced severe austerities and had decided to abstain from marriage . Once he came across a group of men hanging from a tree upside down . These men were his ancestors , who were doomed to misery as their children had not performed their last rites . So they advised Jagatkāru to marry and have a son who could free them of those miseries by performing the ceremonies . Vasuki offered his sister Manasa 's hand to Jagatkāru . Manasa mothered a son , <unk> , who freed his ancestors . Astika also helped in saving the Nāga race from destruction when King Janamejaya decided to exterminate them by sacrificing them in his Yajna , fire offering . 
