Śrīmad-Bhāgavatam · Text 8.7.11
Who is speaking and story frame
तथासुरानाविशदासुरेण
रूपेण तेषां बलवीर्यमीरयन् ।
उद्दीपयन् देवगणांश्च विष्णु-
र्दैवेन नागेन्द्रमबोधरूप: ॥ ११ ॥
tathāsurān āviśad āsureṇa
rūpeṇa teṣāṁ bala-vīryam īrayan
uddīpayan deva-gaṇāṁś ca viṣṇur
daivena nāgendram abodha-rūpaḥ
Thereafter, Lord Viṣṇu entered the demons as the quality of passion, the demigods as the quality of goodness, and Vāsuki as the quality of ignorance to encourage them and increase their various types of strength and energy.
Read Śrīla Prabhupāda's purport on Vedabase.io