In terms of the higher tantras, the deity of meditation (yi-dam lha), who is both wrathful and feminine, is dakini Simhamukha. It is important to understand that despite her very angry appearance and head of an animal, she is not a guardian spirit (srung-ma) who is magically subjugated, turned to the Dharma and bound by oaths of service to some powerful Mahasiddha in the past. Rather, she represents the wrathful manifestation of the Guhyajnana Dakini, who, according to the Nyingma tradition, was Padmasambhava's chief teacher in the land of Oddiyana. Therefore, although Simhamukha is a dakini in her aspect, she functions as a yidam, or meditation deity, and her special functions are to prevent and repel (bzlog-pa) psychic attacks that...
Before he passed into Mahaparinirvana, Buddha Shakyamuni prophesied that in eight (or twelve) years he would send an emanation to continue his activity, protecting the teachings and turning the wheel of Vajrayana.