"The Purana carry on propaganda in favour of a particular deity or a place sacred to that deity, and are sectarian. … The Vayu, Brahmanda, Matsya, and the Vishnu Puranas give ancient royal genealogies. The original Puranas existed long before the Christian era, were revised and modified in later times and chapters on Hindu rites and customs were added to them. They attempted to being Vaishnavism and Saivism within the orthodoxy and combined new doctrines with Vedic rituals, ..."