mano-virya-varotsiktam

 asrnyam akuto-bhayam

bhita nililyire devas

 tarksya-trasta ivahayah

 

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 

 

His mental and bodily strength as well as the boon conferred upon him had made him proud. He feared death at the hands of no one, and there was no checking him. The gods, therefore, were seized with fear at his very sight, and they hid themselves even as snakes hide themselves for fear of Garuda.

 

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 

 

The asuras are generally strongly built, as described here, and therefore their mental condition is very sound, and their prowess is also extraordinary. Hiranyaksa and Hiranyakasipu, having received the boon that they would not be killed by any other living entity within this universe, were almost immortal, and thus they were completely fearless.