Wikipedia
Ekajaṭī or Ekajaṭā, (Sanskrit; "One Plait Woman"), also known as Māhacīnatārā, one of the 21 Taras, is one of the most powerful and fierce goddesses of Indo-Tibetan mythology. According to Tibetan legends she is an acculturation of the pre-Buddhist goddess of heaven, whose right eye was pierced by the tantric master Padmasambhava so that she could much more effectively help him subjugate Tibetan demons.
Ekajati is also known as "Blue Tara". She is generally considered one of the three principal protectors of the Nyingma school along with Rāhula and Vajrasādhu .
Often Ekajati appears as liberator in the mandala of the Green Tara. Along with that her ascribed powers are removing the fear of enemies, spreading joy and removing personal hindrances on the path to enlightenment.
Ekajati is the protector of secret mantras and "as the mother of the mothers of all the Buddhas," represents ultimate unity. As such her own mantra is also secret. She is the most important protector of the Vajrayana teachings, especially the Inner Tantras and termas. As the protector of mantra, she supports the practitioner in deciphering symbolic dakini codes and properly determines appropriate times and circumstances for revealing tantric teachings. Because she completely realizes the texts and mantras under her care, she reminds the practitioner of their preciousness and secrecy. Düsum Khyenpa, 1st Karmapa Lama meditated upon her in early childhood.
According to Namkhai Norbu, Ekajati is the principal guardian of the Dzogchen teachings and is "a personification of the essentially non-dual nature of primordial energy."
Dzogchen is the most closely guarded teaching in Tibetan Buddhism, of which Ekajati is a main guardian as mentioned above. It is said that Sri Singha (Sanskrit: ) himself entrusted the "Heart Essence" teachings to her care. To the great master Longchenpa, who initiated the dissemination of certain Dzogchen teachings, Ekajati offered uncharacteristically personal guidance. In his thirty-second year, Ekajati appeared to Longchenpa, supervising every ritual detail of the Heart Essence of the Dakinis empowerment, insisting on the use of a peacock feather and removing unnecessary basin. When Longchenpa performed the ritual, she nodded her head in approval but corrected his pronunciation. When he recited the mantra, Ekajati admonished him, saying, "Imitate me," and sang it in a strange, harmonious melody in the dakini's language. Later she appeared at the gathering and joyously danced, proclaiming the approval of Padmasambhava and the dakinis.