When the Gods requested Rishi Dhadichi, he sacrificed his body for the welfare of Gods and out of his bones the Gods built a weapon called Vajra. Now the king of the Gods Indra led the other Gods to the battle. Vritra was killed by the gods with a Vajra. Then onwards the Daityas were condemned to live in the watery kingdom of Patala, side by side with the serpent demons, the Nagas.
When the Gods decided to churn the ocean in quest of sacred ambrosia or 'Amrita' to be immortal, they needed the help of the Daityas. The Gods brought a large mountain 'Mandara' from the earth and placed it in the ocean to use it as the churning stick. They used the gigantic snake Vasuki as the churning cord. After Samudramanthan - Daityas were at the left side and Devas at the right side and Lord Vishnu was in the guise of a beautiful lady named Mohini. The Daityas first refused to help the Gods but they were persuaded by the Gods in an intelligent manner. When precious things came out of the ocean, Gods occupied most of them. Even when Amrita came out, the gods took its possession with the help of Lord Vishnu who deceived the Daityas in guise of a beautiful lady, Mohini. Thus the Daityas could not become immortal.
The other story is of Bali, who was the king of Daityas. During the 'Treta' Yuga, the Daityas became powerful again. The Gods went to Vishnu to seek his help. Lord Vishnu came in the guise of a small boy called 'Vaman' and asked three steps of land from Bali. Bali granted it and Vamana becoming a giant put his one leg covering the whole earth, other leg covering the sky and third leg put on Patala. To keep his words king Bali had to give his kingdom. Thus the Gods once again won over their kingdom and saved the universe from the evil forces.
The Bhagavad Gita depicts one such incident, which was considered as most heinous crime at that period. The king of Daityas, Hiranyakashipu wanted to be worshipped like Gods. He tried to prevent his own son Prahlad from making sacrifice to Lord Vishnu. But Prahlad was a great devotee and he did not carry out his father's order saying that God is omniscient and omnipresent and all the worship is due to Hari. Hiranyakashipu was enraged and struck a pillar saying let the god come out from that pillar if he is present everywhere. Hari, a form of Lord Vishnu appeared immediately in the form of half-man and half-lion. He was fierce looking with mane increasing the size of his face, eyes as red as gold burnished in the fire. This form of God is said 'Narasimha' Avatar. Hari caught hold of the Daitya Hiranyakashipu and laid him back over his thigh. He tore his enemy with his sharp nails and made a garland for himself with the enemies Viscera.