I found an article about the wraftful Guardians. Read more below:
An enigmatic aspect of Buddhist iconography is the presence of wrathful, terrifying forms. Though these awesome, hair-raising images seem contradictory to Buddhist ideals, they are not personifications of evil or demonic forces. Rather they symbolize the violence that is a fundamental reality of the cosmos in general, and of the human mind in particular. In addition to destroying the passions of the mind, the purpose of gods is to protect the faithful. The wrathful deities, who symbolize the tremendous effort it takes to vanquish evil, especially perform this function.
An enigmatic aspect of Buddhist iconography is the presence of wrathful, terrifying forms. Though these awesome, hair-raising images seem contradictory to Buddhist ideals, they are not personifications of evil or demonic forces. Rather they symbolize the violence that is a fundamental reality of the cosmos in general, and of the human mind in particular. In addition to destroying the passions of the mind, the purpose of gods is to protect the faithful. The wrathful deities, who symbolize the tremendous effort it takes to vanquish evil, especially perform this function.
In the arena of Buddhist art, the two main classes of objects that constitute our interest are the small bronze sculptures, kept on altars, and the scroll-paintings, better known as thangkas. Both are intended as temporary dwellings for the spiritual, beings into which Buddhism projects its analysis of the nature of the world. They are thus not aesthetic objects but roosting places, actual dwellings for the energies projected into them with the aid of mantras, which are often inscribed on them; the power of those energies can then be canalized towards the Buddhist goal.
Not surprisingly thus, these wrathful deities, though benevolent, are represented in visual arts as hideous and ferocious in order to instil terror in evil spirits which threaten the dharma.
According to the norms of canonical iconography, these wrathful protective deities are described as figures possessing stout bodies, short but thick and strong limbs and many of them have several heads and a great number of hands and feet. The color of their faces and bodies and faces is frequently compared with the characteristic hue of clouds, precious stones, etc. Thus we often read in the Sadhanas (Canonical texts) that one or the other wrathful deity is black “like the cloud which appears at the end of a kalpa (aeon)”, blue “like an emerald” or white “like a mountain of crystal”. The yellow color is compared to that of pure gold, and the red color of some of them is supposed to be “like the hue produced when the sun rises and its rays strike a huge mountain of coral”. These Sadhanas often mention that the body of a ferocious protective deity is smeared with ashes taken from a funeral pyre and with sesame oil or that their skin is covered with grease-stains, blood spots and shining specks of human fat.
Their faces possess a typical wrathful expression: the mouth is contorted to an angry smile, from its corners protrude long fangs – often said to be of copper or iron -, or the upper teeth gnaw the lower lip. A “mist of illnesses” comes forth from the mouth and a terrific storm is supposed to be blowing from the nostrils of the flat nose. The protruding, bloodshot eyes have an angry and staring expression and usually a third eye is visible in the middle of the forehead.
The most important category of these deities is the group of eight, known as Dharampalas (Sans. Dharam: religion; Pala: protector), known in Tibetan as Drag-ched. The Dharampalas, or defenders of Buddhism, are divinities with the rank of Bodhisattva, and are supposed to wage war without any mercy against the demons and enemies of Buddhism.
These eight deities are:
Yama
Mahakala
Yamantaka
Kubera
Hayagriva
Palden Lhamo
Tshangs pa
Begtse
Yama: The God of Death
According to the popular version of the mythological origins of Yama, a holy man was told that if he spent fifty years living in deep meditation in a cave, he would reach enlightenment. On the night of the twenty-ninth day of the eleventh month of the forty-ninth year, two robbers entered his cave with a stolen bull whose head they proceeded to cut off. When they realized that the hermit had witnessed their act, they decided to kill him. He begged them to spare his life, explaining that in a few minutes he would reach enlightenment and that all his efforts would be lost if they killed him before the expiration of the fifty years. The thieves ignored his request and cut off his head. Immediately, he assumed the ferocious form of Yama and put the bull’s head on his own headless body. He then killed the two robbers and drank their blood from cups made from their skulls. In his fury, he threatened to destroy the entire population of Tibet. The Tibetan people appealed to the deity Manjushri (the Bodhisattva of wisdom), to protect them from Yama. Manjushri then assumed the form of Yamantaka (conqueror of death), defeated Yama, and turned him into a protector of Buddhism, in order to save the people.
In visual imagery he is often shown accompanied by his consort, Chamundi, who offers Yama a skull bowl full of demon-blood elixir. He is represented nude, wearing a garland of severed human heads. Dark blue in color he has a buffalo’s head, and is shown in a dynamic position on this animal.
Mahakala: The Great Black One
The legendary history of Mahakala was written by Khedrup Khyungpopa, founder of the Shangpa Kagyu tradition, in the eleventh century. He says that the reason for the special powers and effectiveness of Mahakala goes back to Avalokiteshvara’s vow to remain in the mortal world and not reach Buddhahood until all sentient beings were enlightened. After helping hundreds of thousands of people for countless years to reach enlightenment, Avalokiteshvara saw no decrease in suffering, but rather an increase in defilements. He then became discouraged. As soon as he had that thought, his head immediately split into a thousand pieces. Amitabha, one of the five transcendent Buddhas, put the pieces back together and made eleven heads, telling Avalokiteshvara to make the same promise again but to keep it better. Accordingly out of Avalokiteshvara’s eleven faces, ten are peaceful, but one is wrathful, representing Mahakala.
Avalokiteshvara, saddened, fell unconscious for seven days, after which he thought that the world’s suffering souls needed results in a hurry without excessive effort. He then wished to turn himself into a wrathful deity in order to defeat more rapidly and effectively the obstacles to the happiness of others. With this thought the letter HUM in dark blue color came out of his heart. That Hum became Mahakala. It is not without significance that in the mantra ‘Om Mani Padme Hum’, the syllable Hum invokes energetic powers.
The birth of Mahakala was followed by an earthquake and with one voice the Buddhas in the heaven declared that he would have the power to grant all wishes if the wishes were honest and good.
Mahakala was the personal tutelary deity for the Mongol ruler Kublai Khan. His terrifying imagery ultimately derives from the angry form of the Hindu god Shiva, known as Bhairava. In Tibetan iconography he typically has one head with three bulging eyes. His eyebrows are like small flames, and his beard is made of hook-like shapes. He can have two to six arms.
The essential nature of Mahakala in the Tibetan pantheon can be gauged from the fact that he is worshipped as the Protector of the tent. Because of the nomadic nature of the Tibetan people, much of their life is spent in arduous and hazardous travel, complicated by the generally hostile environment they live in. During their sojourns, they use the Tent as a temporary abode, making it a very important part of their lives. He is also unquestionably the most vital Dharampala, since every monastery, no matter what the order, has a shrine devoted to this deity.
Yamantaka: The Conqueror of Death
Yamantaka, the ferocious emanation of Manjushri (Bodhisattva of wisdom), is the most complicated and terrible of all the wrathful Buddhist divinities. Under this from he conquered the demon king of death, Yama, who was depopulating Tibet in his insatiable thirst for victims. According to this myth, in his paroxysm of insight, Manjushri traveled all the way to the underworld to seek out Yama, the God of death, who dwells with all his minions in the sealed up iron cities of hell. Yama appears in Indian mythology with the head of a water buffalo. To tame Yama, Manjushri adopted the same form, adding to it eight other faces and a multiple array of arms, each holding fearful and deadly weapons. He further sprouted a corresponding number of legs, and surrounded himself with a vast host of terrifying beings. To confront death, he thus manifested the form of death itself, magnified to infinity. Death (Yama) saw himself endlessly mirrored back to himself, infinitely outnumbered by himself. Death was literally scared to death. Thus the yogi who meditates through the imagery of Yamantaka intends and hopes to develop a sense of identity strong enough to face down death, and the fear that attends upon it. Each head, each limb, each attribute, symbol and ornament of Yamantaka expresses the total mobilization of the faculties of enlightenment needed for this ultimate confrontation.
Both Yama and Yamantaka are represented with bull’s heads, but Yama always has an ornament, shaped like a wheel on his breast, which is his distinctive mark.
Source:
http://www.exoticindiaart.com/article/wrathful/