In Tibet, the peacock's remarkable ability to consume poison and transform it into the iridescent hues of its tail is seen as a metaphor for the spiritual process of converting emotions into the spirit of maturity. According to the teachings of Vajrayana, the mental poisons of emotions are neither to be judged as negative nor positive, but are utilized as material on the path to enlightenment. In this volume, Lama Gendün Rinpotsche, one of the most significant masters of Tibetan Buddhism, provides insights into the techniques of Vajrayana mind training. The teachings are based on a classic work from the 17th century, the Mountain Teachings of Chagme Rinpotsche. Karma Chagme Rinpotsche, born in 1613, is regarded as one of the highest yogis and scholars of Tibet. He authored many teachings to assist all practitioners on the path of Dharma, which encompass more than a hundred volumes. The Mountain Teachings represent the essence of all his instructions. This third edition is a slightly revised version of the first two editions. For the third edition, some passages that were included in the English version but were overlooked in previous editions have been translated and added, and errors have been corrected. The footnotes and glossary have been updated, and the terminology has been adapted to contemporary usage.