Heruka
Heruka (Sanskrit; Tibetan: ), is the name of a category of wrathful deities, enlightened beings in Vajrayana Buddhism that adopt a fierce countenance to benefit sentient beings. In East Asia, these are called Wisdom Kings. "Herukas" represent the embodiment of indivisible bliss and emptiness. They appear as "Iṣṭha-devatā" (Tibetan: ) or meditational deities for tantric sādhanā, usually placed in a "mandala" and often appearing in "Yab-Yum". Derivation and meaning of the term. Heruka represents wrathful imagery with indivisible emptiness (śūnyatā), bliss, peace, wisdom, compassion (bodhicitta), and love. Herukas represent unified consciousness, with emptiness being a reflection of "non-phenomena  or emptiness which is all love," or removal of imagery to reach universal love, mercy, and compassion-mind. Interpretation of Heruka is similar to the female ḍākiṇī or buddha Vajrayogini. The Sanskrit term Heruka was translated into both Chinese and Tibetan as "blood drinker," which scholar Ronald Davidson calls "curious," speculating that the nonliteral translation derived from an association the term has with cremation grounds and 'charnel grounds' (Sanskrit: "śmāśāna") (which absorb the blood of the dead). Sanskrit terms for blood drinker include "asrikpa", reflecting a Sanskrit word for blood ("asrik"), and "raktapa", "raktapayin", or "rakshasa", derived from an alternate  root term for blood ("rakta"). Unlike the Chinese and Tibetan (', wylie: ') terms used to translate it, the Sanskrit term heruka does not literally mean blood drinker, although the fact that it was rendered as such into two other languages strongly suggests an according Indian interpretive etymology. Eight Herukas of the Nyingma Mahayoga. The eight "Herukas" (Wylie: "sgrub pa bka’ brgyad") of the Nyingma mahayoga tradition (and their corresponding sadhanas) are said to have been received by "Padmakara" from the Eight "Vidyadharas" (Tib. "Rigdzin"), or Eight Great "Acharyas": Manjushrimitra, Nagarjuna, Vajrahumkara, Vimalamitra, Prabhahasti, Dhanasamskrita, Shintamgarbha and Guhyachandra. They were proficient in  the practices of, respectively: 1) Yamantaka (Tib. ', ') the wrathful Manjushri, the deity of body; 2) Hayagriva (Tib. "Pema Sung", "") the wrathful Avalokiteśvara, the deity of speech; 3) Vishuddha/Sri Samyak (Tib. "Yangdak Thuk", Wylie: "") the wrathful Vajrapani deity of mind; 4) Mahottara (Tib. "Chem Chok", Wylie: "") the wrathful Samantabhadra, the deity of enlightened qualities; 5) Vajrakilaya/Vajrakumara (Tib. ', '), the wrathful Vajrasattva, the deity of purification; 6) Matarah (Tib. "Mamo Botong", "") the wrathful Akasagarbha, the deity of calling and dispatching; 7) Lokastotrapuja-natha (Tib. ', ') the wrathful Ksitigarbha, the deity of worldly offering and praise; 8) Vajramantrabhiru (Tib. ', ') the wrathful Maitreya, the  deity of wrathful mantras. "Padmasambhava" is quoted in the Bardo Thodol (Antarabhavatantra - "Tibetan Book of the Dead"): "The crucial point is indeed that those who have meditated on the formal description of these Herukakaya ('bodies of Heruka'), and also made offerings and praise to them, or, at the very least, have simply seen their painted and sculpted images, may recognise the forms that arise here and attain moksha (liberation)."