ḍākinī figures appear in Hinduism and Bon, ḍākinīs occur most notably in Vajrayana Buddhism and especially Tibetan Buddhism. The khandroma, generally of volatile or wrathful temperament, acts somewhat as spiritual muse for spiritual practice. Dakinis are energetic beings in female form, evocative of the movement of energy in space. In this context, the sky or space indicates śūnyatā, the insubstantiality of all phenomena, which is, at the same time, the pure potentiality for all possible manifestations. The ḍākinī appears in a Vajrayana formulation of the Buddhist refuge formula known as the Three Roots. Sometimes she appears as the dharmapala, alongside a guru and yidam. An archetypal ḍākinī in Tibetan Buddhism is Yeshe Tsogyal, consort of Padmasambhava. Classes of ḍākinī Judith Simmer-Brown, based on teachings she received from Tibetan lamas, identifies four main classes of ḍākinī. These follow the twilight language tradition of esoteric Buddhism in referring to secret, inner, outer and outer-outer classes of ḍākinīs. The secret class of ḍākinī is prajnaparamita (Tibetan yum chenmo), the empty nature of reality according to Mahayana doctrine. The inner class of ḍākinī is the ḍākinī of the mandala, a meditational deity (Tibetan:yidam) and fully enlightened Buddha who helps the practitioner recognise their own Buddhahood. The outer ḍākinī is the physical form of the ḍākinī, attained through completion stage tantra practices such as the Six Yogas of Naropa that work with the subtle winds of the subtle body so that the practitioner's body is compatible with an enlightened mind. The outer-outer ḍākinī is a ḍākinī in human form. She is a yogini in her own right but may also be a karmamudrā, or consort, of a yogi or mahasiddha. Dakinis can also be classified according to the Trikaya, or three bodies of buddhahood. The Dharmakāya ḍākinī, which is Samantabhadrī, represents the dharmadhatu where all phenomena appear. The Sambhogakāya ḍākinīs are the yidams used as meditational deities for tantric practice. The Nirmanakāya ḍākinīs are human women born with special potentialities; these are realized yoginis, consorts of gurus, or even all women in general as they may be classified into the Five Buddha Families. Daka In some instances, the terms ḍāka and ḍākinī have been used for practitioners of tantric yoga themselves. In other instances, just ḍākinī was used for female practitioners, while male practitioners were just known as yogi. Padmasambhava was known as a yogi and Yeshe Tsogyal, a Tibetan princess, yogini and consort of