sura-dvisam sriyam guptam
vaisnavya vidyaya vibhuh
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The opulence of the demons, who are generally known as the enemies of the demigods, was protected by the talents and tactics of Sukracarya, but Visvarupa, who was most powerful, composed a protective prayer known as the Narayana-kavaca. By this intelligent mantra, he took away the opulence of the demons and gave it to Mahendra, the King of heaven.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The distinction between the demigods (devas) and demons (asuras) is that the demigods are all devotees of Lord Visnu whereas the demons are devotees of demigods like Lord Siva, Goddess Kali and Goddess Durga. Sometimes the demons are also devotees of Lord Brahma. For example, Hiranyakasipu was a devotee of Lord Brahma, Ravana was a devotee of Lord Siva, and Mahisasura was a devotee of Goddess Durga. The demigods are devotees of Lord Visnu (visnu-bhaktah smrto daiva), whereas the demons (asuras tad-viparyayah) are always against the visnu-bhaktas, or Vaisnavas. To oppose the Vaisnavas, the demons become devotees of Lord Siva, Lord Brahma, Kali, Durga, and so on. In the days of yore, many long years ago, there was animosity between the devas and the asuras, and the same spirit still continues, for the devotees of Lord Siva and Goddess Durga are always envious of Vaisnavas, who are devotees of Lord Visnu. This strain between the devotees of Lord Siva and Lord Visnu has always existed. In the higher planetary systems, fights between the demons and the demigods continue for a long, long time.
Herein we see that Visvarupa made for the demigods a protective covering, saturated with a Visnu mantra. Sometimes the Visnu mantra is called Visnu-jvara, and the Siva mantra is called Siva-jvara. We find in the sastras that sometimes the Siva-jvara and Visnu-jvara are employed in the fights between the demons and the demigods.
The word sura-dvisam, which in this verse means “of the enemies of the demigods,” also refers to the atheists. Srimad-Bhagavatam elsewhere says that Lord Buddha appeared for the purpose of bewildering the demons or atheists. The Supreme Personality of Godhead always awards His benediction to devotees. The Lord Himself confirms this in Bhagavad-gita (9.31):
na me bhaktah pranasyati
“O son of Kunti, declare it boldly that My devotee never perishes.”