Diti, being the mother of the asuras, sought revenge for the deaths of her children by the hands of the devas.
Diti is said to have undergone severe austerities for ten thousand years in exchange for a boon which granted her a child who would slay the devas.
Consenting, Kashyapa granted his wife Vajranga, possessing adamantine limbs, who performed her bidding by capturing Indra and the devas and punishing them.
When Aditi protested, Brahma urged Vajranga to release his captives, who acquiesced, stating that he had only done what his mother had instructed.
When he offered her a boon, she asked him to grant her a son who would capture the three worlds, and cause misery to the devas.