Bies (pronounced [ˈbjes]) or bes (Russian: бес [ˈbʲes]) is an evil spirit or demon in Slavic mythology.
The word is synonimous with chort.
After the acceptance of Christianity the bies became identified with the devil, corresponding to the being referred to in Ancient Greek, as either daimon (δαίμων), daimónion or pneuma (πνεῦμα). For example, biesy (Russian plural of bies) is used in the standard Russian translation of Mark 5:12, where we have the devils entering into the swine in KJV. Compare to the Ukrainian bisy (used always in plural) or bisytysia (to go mad).