Guhyasamaja is one of the oldest and most highly regarded Anuttarayoga Tantras, or highest Tibetan yoga practices. Most closely associated with the Gelug and Shakya lineages, Guhyasamaja is called a “father tantra,” because it is concerned with the development of the masculine “method,” or skillful means. Its extensive practices relating to bliss and the illusory body include esoteric symbolism and complex meditations, mantras, and rituals.