In her previous birth, Manthara was a Yakshini (celestial being). The king of Kaikey was out on a hunt and his arrow killed a deer. The doe, his wife, ran weeping to her mother. Unable to bear the sorrow of her daughter doe, the Yakshini asked the king to give the dead deer to her. "I am a Yakshini, I can restore him to life", she said.
But the young king would not heed her request and struck her with his sword. The dying words of the Yakshini were a dreadful curse. "Just as you have caused the death of my innocent son-in-law, so too, I will be responsible for the death of your son-in-law. It was this Yakshini who was born as Manthara. She was also the gandharvi (celestial being) named Dundubhi, while in one life she was Manthara, in another she was the servant called Kubja in the kingdom of Kamsa.
It is also said Saraswati sat on Manthra;s tongue whilst poisoning Kaikei's mind...