In the tantras, there are various fierce deities which are tantric forms of the Buddhas. These may be fierce (Tibetan: "trowo", Sanskrit: "krodha") Buddha forms or semi-fierce, and may appear in sexual union with a female Buddha or as a "solitary hero". The Herukas (Tb. "khrag 'thung", lit. "blood drinker") are enlightened masculine beings who adopt fierce forms to help beings. They include Yamantaka, Cakrasamvara, Hevajra, Mahākāla, and Vajrakilaya. Dakinis (Tb. "khandroma", "sky-goer") are their feminine counterparts, sometimes depicted with a heruka and sometimes as independent deities. The most prevalent wrathful dakinis are Vajrayogini, Vajravārāhī, Nairatmya, and Kurukullā.