martasya te hy amartasya
darśanaṁ nāphalaṁ mama
It appears that human beings and asuras are subject to death, whereas demigods are not. The demigods who reside with Lord Brahmā in Satyaloka go to Vaikuṇṭhaloka in their present bodily constructions at the time of the dissolution. Therefore although Hiraṇyakaśipu had undergone severe austerities, Lord Brahmā predicted that he had to die; he could not become immortal or even gain equal status with the demigods. The great austerities and penances he had performed for so many years could not give him protection from death. This was foretold by Lord Brahmā.