In Vajrayana Buddhism, a dharmapāla (Wylie: chos skyong) is a type of wrathful deity. The name means "Dharma-defender" in Sanskrit, and the dharmapālas are also known as the Defenders of the Law (Dharma), or the Protectors of the Law, in English.
In Vajrayana iconography and thangka depictions, dharmapālas are fearsome beings, often with many heads, many hands, or many feet. Dharmapālas often have blue, black or red skin, and a fierce expression with protruding fangs. Though dharmapālas have a terrifying appearance and countenance, they are all bodhisattvas or buddhas, meaning that they are embodiments of compassion that act in a wrathful way for the benefit of sentient beings.
In Tibet, principal Dharmapalas include:
Mahakala (Tib. Nagpo Chenpo), Yama (Tib. Shinje), Yamantaka (Tib. Shinje Shed), Hayagriva (Tib. Tamdrin), Vaisravana (Tib. Kubera),
Shri Devi (Tib. Palden Lhamo), Ekajati (Tib. ral chig ma), Rahula (Tib. gza), Vajrasadhu (Tib. Dorje Legpa), Tshangs Pa Dkarpo, Prana Atma (Tib. Begtse).
In Tibet, most monasteries have a dedicated dharmapāla which was originally comparable to a genius loci. The many forms of Mahakala, for example, are emanations of Avalokiteshvara. Kalarupa, Yamantaka and Shri Devi (Tib. Palden Lhamo) are considered by practitioners to be emanations of the Buddha of Wisdom (Manjushri).
The main functions of a dharmapāla are said to be to avert the inner and outer obstacles that prevent spiritual practitioners from attaining spiritual realizations, as well as to foster the necessary conditions for their practice.
In Japan, the dharmapāla Yamantaka (Daiitoku) is classified as a Wisdom King. Some other dharmapālas, notably Mahakala (Daikoku), belong to the fourth hierarchy of deities (tenbu). (Wikipedia)
#1: Mahakala: typically black in color & depicted with a crown of five skulls
Reference: Mahakala
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#3: Mahakala trampling the elephant-headed figure of Ganesha."
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#5: Hayagriva: with a human body and a horse's head or a horse head in his hair,
Reference: Hayagriva
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#6: Hayagriva: often with his right hand either blessing the supplicant or in the vyaakhyaa mudraa pose of teaching. The right hand also usually holds a aksha-maalaa (rosary), indicating his identification with meditative knowledge. His left holds a book, indicating his role as a teacher.
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#7: Hayagriva, Tibet 15th century CE Bronze: depicting Hayagriva, a fierce form of the compassionate Avalokiteshvara, with three faces, six arms and four legs and horse heads in his hair
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#8a: sri-hayagriva: In Hinduism, Hayagriva is often depicted with a human body and a horse's head
#8b: Yogini Hayagriva Seated Holding a Child (Yogini is the feminine form corresponding to the masculine yogi)
Image source: 4krsna.wordpress.com: sri-hayagriva→
wikimedia.org commons.wikimedia.org: Yogini Hayagriva
#11: Palden Lhamo as depicted in a thangka from the Potala Palace, Lhasa
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#12: Palden Lhamo Central Tibet 15th century, Gilt-copper, pigment, and semiprecious stones
Image source: commons.wikimedia.org
Palden Lhamo is the only female among the traditional 'Eight Guardians of the Law' and is usually depicted as deep blue in colour and with red hair to symbolise her wrathful nature, crossing a sea of blood riding side-saddle on a white mule. The mule has an eye on its left rump where her angry husband's arrow hit it after she killed her son and used his skin as a saddle blanket, before she became converted to a protector of the dharma. She is considered to be a form of the Hindu goddess Mahakali and also a wrathful emanation of Saraswati. She has three eyes and is often shown drinking blood from a human skull.
Ekajati is of a blue skin tone, with a high, red chignon ("she who has but one chignon" is another one of her titles). She has one head, one breast, two hands and a third eye. However, she can also be depicted with more body parts; up to twelve heads and twenty four arms, with different tantric attributes (sword, kukuri, phurba, blue lotus axe, vajra). In her most common form she holds an axe, drigug (cleaver) or khatvanga (tantric staff) and a skull cup in her hands. In her chignon is a picture of Akshobhya. Her demeanour expresses determination. With her right foot she steps upon corpses, symbols of the ego. Her vajra laugh bares a split tongue or a forked tongue and a single tooth. She is dressed in a skull necklace and with a tiger and a human skin. She is surrounded by flames representing wisdom.-----Wikipedia: Ekajati
Her single tuft of hair, eye, tooth, and breast, are symbolic of non-duality. She wears a cloud as a garment to indicate that she dwells within the expanse of the sky. In her right hand she wields a human corpse as a symbol that duality destroys itself of itself and with itself. In her left hand she holds a ripped out human heart – the uncompassionately murdered heart of aggressive self-justification. She tramples on the corpse of duality. In this depiction she wears the human bone cemetery ornaments and the tiger skin skirt of a yidam – to display her mastery of all enlightened activities. -----aroencyclopaedia.org
Rahula (Tib. kyab jug) is the most wrathful of the oath-bound protectors. Fiercely wrathful, purple-black in color, with nine heads. Each face has three large eyes and a gaping mouth with exposed fangs. On his stomach is the large face of the original Rahula who devoured the nine celestial planets. His body is covered with numerous eyes indicating that he is protecting the Dharma in all ten directions.-----www.prayerflags.com
The three principle protectors of the Nyingma lineage are said to be Ekajati , Rahula and Vajrasadhu.