kṛtāvanāmāḥ prayayus tri-viṣṭapam
sahasraśīrṣāpi tato garutmatā
madhor vanaṁ bhṛtya-didṛkṣayā gataḥ
The word sahasraśīrṣā refers to the Personality of Godhead known as Garbhodakaśāyī Viṣṇu. Although the Lord appeared as Kṣīrodakaśāyī Viṣṇu, He has been described here as Sahasraśīrṣā Viṣṇu because He is nondifferent from Garbhodakaśāyī Viṣṇu. According to Śrīla Rūpa Gosvāmī in his Laghu-bhāgavatāmṛta, the Sahasraśīrṣā Personality of Godhead who appeared at that time was the incarnation known as Pṛśnigarbha. He created the planet known as Dhruvaloka for the habitation of Dhruva Mahārāja.