In Vaishnava mythology, such as is presented in the Bhagavata Purana and the Pancaratra, whenever the cosmos is in crisis, typically because the evil has grown stronger and has thrown the cosmos out of its balance, an avatar of Vishnu appears in a material form, to destroy evil and its sources, and restore the cosmic balance between the everpresent forces of good and evil. The most known and celebrated avatars of Vishnu, within the Vaishnavism traditions of Hinduism, are Krishna, Rama, Narayana and Vasudeva. These names have extensive literature associated with them, each has its own characteristics, legends and associated arts. The Mahabharata, for example, includes Krishna, while the Ramayana includes Rama.