Dromton's teacher was the disciple of a man who was one of how many Buddhist Mahasiddhas?
Ratnākaraśānti: Ratnākaraśānti (also known as Śāntipa) (c. 1000 CE) was one of the eighty-four Buddhist Mahāsiddhas and the chief debate-master at the monastic university of Vikramashila. Atiśa:  He is recognised as one of the greatest figures of classical Buddhism, and Atisa's chief disciple Dromtön was the founder of the Kadam School.
eighty-four