Formerly, there was a devastating war between the demigods and the demons. The demigods, having been defeated, accepted Purañjaya as their assistant and then conquered the demons. Therefore this hero is known as Purañjaya, “he who conquered the residence of the demons.”
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
कृतान्त आसीत्समरो देवानां सह दानवैः । पार्ष्णिग्राहो वृतो वीरो देवैर्दैत्यपराजितैः
kṛtānta āsītsamaro devānāṃ saha dānavaiḥ | pārṣṇigrāho vṛto vīro devairdaityaparājitaiḥ
SB 9.6.13