While the view of the Vajrayana was based on Madhyamaka, Yogacara and Buddha-nature theories, it saw itself as being a faster vehicle to liberation containing many skillful methods (upaya) of tantric ritual. The need for an explication and defense of the Tantras arose out of the unusual nature of the rituals associated with them, which included the use of secret mantras, alcohol, sexual yoga, complex visualizations of mandalas filled with wrathful deities and other practices and injunctions which were discordant with or at least novel in comparison to traditional Buddhist thought. The Guhyasamāja Tantra, for example, states: "you should kill living beings, speak lying words, take things that are not given and have sex with many women". Other features of tantra included a focus on the physical body as the means to liberation and a reaffirmation of feminine elements, feminine deities and sexuality.