This person was Dhanvantari, a plenary portion of a plenary portion of Lord Viṣṇu. He was very conversant with the science of medicine, and as one of the demigods he was permitted to take a share in sacrifices.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
अमृतापूर्णकलशं बिभ्रद्वलयभूषितः । स वै भगवतः साक्षाद्विष्णोरंशांशसम्भवः
amṛtāpūrṇakalaśaṃ bibhradvalayabhūṣitaḥ | sa vai bhagavataḥ sākṣādviṣṇoraṃśāṃśasambhavaḥ
SB 8.8.34