Panchen Sonam Dragpa was unique in having served as abbot of the three main Gelug monasteries – Ganden, Sera and Drepung.
[5] Panchen Sonam Dragpa's collected works spans fourteen volumes, constituting the main textbooks still used today in the educational curriculum for "the Loseling College, the Shartse College of the Ganden Monastic University, in many monasteries of Kham and Amdo provinces of Tibet as well as in some monasteries in Mongolia.
"[7] Dr. Ursula Bernis summarizes Panchen Sonam Dragpa's accomplishments: "a great master, writer, abbot of all monastic universities in turn, vajrayana adept, whose textbooks are still today used at Drepung" and "the teacher of two Dalai Lamas.
[13] In 1539, Panchen Sonam Dragpa was enthroned as the first tulku of the Upper Chamber (Zimkhang Gong, Wylie: gzims-khang gong-ma[14]) at Drepung Monastery.
[15] This reincarnation lineage is thought to have ended with the violent death of Tulku Dragpa Gyaltsen (1619-1656), but followed by his manifestation as the Dharma Protector Dorje Shugden.