Mahayoga (rnal 'byor chen po)

Mahayoga - The first of the 'Three Inner Tantras.' Mahayoga as scripture is divided into two parts: Tantra Section and Sadhana Section. The Tantra Section consists of the Eighteen Mahayoga Tantras while the Sadhana Section is comprised of the Eight Sadhana Teachings. Jamgon Kongtrul says in his Treasury of Knowledge: "Mahayoga emphasizes means (upaya), the development stage, and the view that liberation is attained through growing accustomed to the insight into the nature of the indivisibility of the superior two truths." The superior two truths in Mahayoga are purity and equality — the pure natures of the aggregates, elements and sense factors are the male and female buddhas and bodhisattvas. At the same time, everything that appears and exists is of the equal nature of emptiness.

from the Glossary to Advice from the Lotus-Born

Eighteen Mahayoga Tantras (ma ha yo ga’i rgyud sde bco brgyad). Listed in Chapter Twelve of The Lotus-Born. An alternative list is given by Shechen Gyaltsab in his historical work entitled The Pond of White Lotus Flowers and in Guru Tashi Tobgyal’s Ocean of Wondrous Sayings to Delight the Learned Ones: 1-5) Five Basic Root Tantras of Body, Speech, Mind, Quality and Activity: Sarvabuddha Samayoga, Assemblage of Secrets, Glorious Supreme Primal Tantra, and Activity Garland. 6-10) Five Display Tantras functioning as utilization of sadhana practice: Heruka Display Tantra, Supreme Steed Display Tantra, Compassion Display Tantra, Nectar Display Tantra, and Twelvefold Kilaya Tantra. 11-15) Five Tantras Functioning as Subsidiaries to Conduct: Mountain Pile, Awesome Wisdom Lightning, Arrangement of Samaya, One-pointed Samadhi, and the Rampant Elephant Tantra. 16-17) Two subsequent tantras of amending incompleteness: Magical Net of Vairochana and Skillful Lasso. 18) The one outstanding tantra that epitomizes them all: The Essence of Secrets, the Tantra of the Magical Net of Vajrasattva, also known as Guhyagarbha.

from the Glossary to The Lotus-Born