Ha-Sa is the pathway breath takes in living creatures. This mantra exists in the form of exhalation and inhalation, dearest one. Just as clouds cannot exist without wind, and just as the sky is without limit, so the world cannot exist except by (this) Shri Paraprasada mantra. The world of immovable and moving things comes from the Shri Paraprasada mantra - Kularnavatantra III
The Devi Kali has many forms. Kashmir Shaivism speaks of twelve Kalis, while in other parts of India she is and was worshipped as Mahakali, Dakshina Kalika, Shmashanakali, Bhadrakali, Kamakali, and Guhyakali, amongst many others.
The Guhyakalika section (khanda) of Mahakalasamhita is a voluminous work, comprising many thousands of shlokas (verses) and with Guhyakalika (Secret Kalika) as its focus. But the work also covers a number of other tantrik topics in equally great detail, and along the way also includes subjects rarely referred to in other published tantras.
The work follows the usual tantrik formula, with Mahakala answering questions posed to him by his spouse, Kali.
Mahakala opens the Guhyakali section of the Mahakalasamhita by saying he will reveal the mantra, yantras, meditation forms (dhyana and rules of worship relating to Guhyakali, which, he says, have been previously hidden. There are eighteen Guhyakali mantras, he says.
Guhyakali, he says, has forms with 100, 60, 36, 30, 20, 10, five, three, two and one faces. Different mantras correspond to these different forms, which he then reveals, using the usual codes for the different letters of the Sanskrit alphabet employed in other tantras.
Mahakala starts to talk about Guhyakali when she is on her lion seat (simhasana), and gives meditations for the guardians of the directions (dikpala), and the five great corpses, forms of Shiva, upon which she sits. There is a sixth pitha, Bhairava. He is described as black in colour, with four arms, terrifying and the cause of fear. He has five faces, each with three eyes. In his left hands he holds a skull staff khatvanga and scissors, and in his right a skull and the hourglass shaped damaru. He is adorned with a garland of skulls, and is fanged. Lying, on an eight petalled lotus above Bhairava is a two-armed form of Shiva, clothed in tiger skin and holding a skull-staff and a trident. The four petals of the major directions represent dharma (duty), jnana (knowledge), vairagya (dispassion) and aishvarya (dominion).
The 10-faced form of Guhyakali is then described. She has 27 eyes, with some faces having two, and other three, eyes. Each of her faces represents a different female animal aspect of Guhyakali and is of a different hue. For example, her upper face is called Dvipika (a leopard or possibly a panther), then comes Keshari (a lion) which is white, Pheru ( jackal) which is black, then Vanara (a monkey) which is red, Riksha (a bear) which is purple, Nara (a woman) which is of a cochineal colour, Garuda which tawny, Makara (a crocodile) which is turmeric colour (yellow), Gaja (elephant) which is of a golden colour, and Haya (horse) which is of a dark or dusky (shyama) colour.
The human face is on Guhyakali's shoulders. To the left of that face is the crocodile, above that the horse and above that the bear. To the right of her face is the Garuda, the elephant, and the monkey. On the top of her head is the monkey face, above that the lioness face, and above that the leopardess.
Guhyakali's human face has great, fierce sharp fangs, she laughs very loudly, while streams of blood pour from her mouth. She has a rolling tongue and is adorned with garlands of skulls, with earrings also of skulls. The mother of the universe (jagadambika) has 54 arms each of which holds a weapon. Her right hands hold a jewelled rosary, a skull, a shield, a noose, a shakti missile, a skull-staff, a bhushundi weapon, a bow, a discus, a bell, a young corpse, a mongoose (?), a rock, a man's skeleton, a bamboo stave, a serpent, a plough, a fire hearth, a damaru, an iron mace, a small spear (bhindipala -- it could mean a sling), a hammer, a spear, a barbed hook, a club studded with metal nails (shataghni). Her right hands hold a jewelled rosary, scissors, make the gestures (mudra) of threatening, a goad, a danda, a jewelled pot, a trident, five arrows and so forth.
In the same work there is a nyasa specifically for the 10 faces of this form of the goddess. Here, the faces are related to the 1,000 petalled lotus, the mouth, the right eye, the left eye, the right nostril, the left nostril, the right cheek, the left cheek, the right ear and the left ear.
Guhyakali has three major forms, corresponding to creation, maintenance and destruction, a little like a very much darker form of Tripurasundari.
Chapter five of the Guhyakalikhanda describes 18 yantras of the Devi, corresponding to the 18 separate mantras mentioned earlier.
The first consists of a bindu, a triangle, a hexagon, a pentagon, a circle, 16 petals, eight petals and four doors, adorned with tridents and skulls. This relates to Guhyakali's one letter mantra, which is Phrem (see above left).
Guhyakali dwells within the centre of eight cremation grounds (shmashans), whose names are Mahaghora, Kaladanda, Jvalakula, Chandapasha, Kapalika, Dhumakula, Bhimangara, and Bhutanatha. Her worship honours the Vetalas (vampires), eight tridents, vajras, jackals and corpses, Bhairavas, dakinis, Chamundas, Kshetrapalas, Ganapatis and other denizens of the cremation ground.
Taken from: http://www.shivashakti.com/guhya.htm