Indian mythology · asura · invulnerability by technicality
The demon whose boon allowed death only at the hands of a son of Shiva, secure while the great ascetic remained unwed. The gods' entire campaign to marry Shiva to Parvati exists to produce his destroyer, Kartikeya.
Only a son of Shiva can kill the demon Taraka, and Shiva has been in meditation since Kamadeva burned for interrupting him. Parvati's austerity finally wins the god; the child's unbearable seed passes through Agni and Ganga to be born as six-faced Kartikeya, who takes command of heaven's armies and ends Taraka.