Śrīmad-Bhāgavatam · Text 4.18.21
Who is speaking and story frame
यक्षरक्षांसि भूतानि पिशाचा: पिशिताशना: ।
भूतेशवत्सा दुदुहु: कपाले क्षतजासवम् ॥ २१ ॥
yakṣa-rakṣāṁsi bhūtāni
piśācāḥ piśitāśanāḥ
bhūteśa-vatsā duduhuḥ
kapāle kṣatajāsavam
Then the Yakṣas, Rākṣasas, ghosts and witches, who are habituated to eating flesh, transformed Lord Śiva’s incarnation Rudra [Bhūtanātha] into a calf and milked out beverages made of blood and put them in a pot made of skulls.
Read Śrīla Prabhupāda's purport on Vedabase.io