Most people only know the childhood of Prahlada, who was rescued from his from Hiranyakashipu by Vishnu's incarnation. What is less well-known, however, Prahlada's adulthood. As king of the Asuras, Prahlada was a formidable enemy of the gods, and he even managed to conquer Devaloka, although Indra was able to get it back through trickery as I discuss here. But through all of this he still maintained the noble character of his childhood; he was the one who inculcated devotion to Vishnu in his grandson Mahabali. And when Mahabali was defeated by Vishnu's incarnation Vamana, both Prahlada went along with Mahabali to Patalaloka, and he later attained Moksha.
But now I've come across across incident in Prahlada's life. I found it in this excerpt from the Prabhasa Kanda of the Skanda Purana, which discusses how long different demons ruled the three worlds for:
Hiranyakashipu shone as the king for one hundred seven million two hundred eighty thousand years. He was the emperor of the three worlds.... After his term was over, Bali became the king for ten million three hundred sixty thousand years. When Bali continued to be the king, Prahlada was held as hostage by the Suras. Indra and other famous (Suras) killed the Asuras with their valour. The rule of the Daityas continued thus for ten Yugas without any enemy. Then for eighteen Yugas, the entire region of the three worlds was protected carefully by Mahendra.
My question is, what is the story of Prahlada being held hostage by the gods during Mahabali's reign? How was he taken hostage, and how was he freed?
He must have been freed, because Prahlada was present during Mahabali's encounter with Vamana. So did Mahabali mounted a rescue mission for his grandfather, or did he pay the gods a ransom, or what?