From the translator's introduction:

This book is a translation of a short collection of the songs and teachings of the first Traleg Kyabgon Rinpoche, Nyima Tashi. It is not a biography in the usual sense of the word, and in fact little is known about Nyima Tashi's life. He is said to have lived at the time of Chodrak Gyamtso, the seventh Gyalwang Karmapa (1454-1505), who is said to have been his guru.

The Traleg Kyabgons have been principal lineage holders of Thrangu Monastery, a major monastery of the Karma Kagyu tradition in Eastern Tibet, since the sixteenth century. Before then, in fact before the name Traleg Kyabgon was given to this succession of incarnations, this holy being served the Buddha's teachings and demonstrated the achievement of awakening time after time under many names.

This book tells us about several of these prior incarnations. In essence, the Traleg Kyabgon is the bodhisattva Vajrapani, the personification of the power of all buddhas. The title Kyabgon, Refuge and Protector, is no exaggeration.