The tantra of the Glorious Secret Essence (the Guhyagarbha Tantra) primarily belongs to the category of Mahayoga. It is taught that this Secret Essence Tantra extracts the essence of the eighteen Mahayoga tantras as well as being the general tantra of enlightened mind. The twenty-two chapters of this tantra afford an explanation of the three tantras of the ground path and result and within the context of the tantra of the path, the ten topics of tantra.
As the author Dodrupchen Tenpa'i Nyima himself has said, this glorious Secret Essence Tantra possesses eight great features. It is the king of all tantras, pinnacle of all vehicles, origin of all doctrines, general commentary for all scriptural transmissions, core wisdom, intent of all the victorious ones, ultimate state of all results, path that all tathagatas have embarked upon, and great path of all true practitioners. Commentary to the Guhyagarbha Tantra, the Key to the Precious Treasury, synthesizes the meaning of all eighteen Mahayoga tantras from the perspective of the author's personal realization and authoritative scholarship. As the means through which serious practitioners can realize the truth of inseparable purity and evenness, this teaching is the guide for knowing how to internalize the Secret Mantra path of the generation and completion stages.
"Dodrupchen Jigme Tenpa'i Nyima was a master of almost inconceivable brilliance and realization who devoted his entire life to spiritual practice. Perhaps the most important of his remarkable writings and one that is frequently cited by His Holiness the Dalai Lama is Key to the Precious Treasury, which unlocks the profound and subtle points of view, meditation, and action in the Secret Essence Tantra according to the ancient Zur tradition. This English version, translated with the blessing and guidance of the learned Khenchen Namdrol, will be welcomed by all serious students of the Vajrayana."—Sogyal Rinpoche, author of The Tibetan Book of Living and Dying
"Key to the Precious Treasury is one of the most important treatises on the cycle of the Secret Essence Tantra composed by one of the greatest luminaries of Tibet, Jigme Tenpa'i Nyima, the Third Dodrupchen Rinpoche (1865–1926). Key to the Precious Treasury elucidates the view of the Secret Essence that sees all existence encompassed within the two extraordinary truths. In genuine truth, the aspect of luminosity free from conceptual elaborations is ultimate basic space. The aspect of natural clarity, free from obscurations, is ultimate wisdom. The aspect of being the treasury of body, speech, mind, qualities, and actions of buddhahood is the ultimate result. In relative truth the world and beings arise as infinite purity—the magical manifestation of actual genuine truth. In their true nature the two truths are nondual—indivisible. Key to the Precious Treasury further details the ten esoteric trainings taught in the Secret Essence. They are the profound view of the nature as it is conduct mandala empowerment root and branch samayas enlightened activity common and uncommon accomplishment unwavering samadhi offering and mantra and mudra. Followers of inner esoteric Buddhist teachings should study Key to the Precious Treasury slowly and repeatedly and enshrine it on their meditation altars as a source of wisdom and blessing."—Tulku Thondup Rinpoche, The Buddhayana Foundation