Bies (read: b-yes) - in Slavic mythology, demoniacal, obsessional bad spirit, demon, after acceptance of Christianity identified with devil, translating Greek: daimon, daimónion, pneuma;

OldSlav. *besъ:

1. ProtoSlav. *boids < IE. *bhoidh-sos "causing fear, horror(?)" - compare to Lith. baisŕ „fear", baisůs „terrified", baisétis „to be afraid", or

2. IE. *bhe-sos - with the same core as in belъ(< bhe-l-os) "white", so it means „shining, luminous".

There is probable hypothesis (splendidly explaining semantic differences) joining "bies" with substance (= spirit) causing madness, prophetic ecstasy with "logorrhoea". This supposition is based on the ground of interpretation word "biesiada" (Pl.) ("a treat; conversation") as OldSlav. *bes-eda < ProtoSlav. *bhes-ed-a „bies(=food lighting up a mind)-eating, " (A. Bankowski) (see "Luci-fer"), so the sense: "a (ritual) treat, feast" and "conversation" is derived from ritual recitation or conversation with other world, compare to Greek "dialektike" in the most original meaning of this word ("a conversation with god during Apollinian profetic rage”); see also: Sanskr. bhasa „a light", bhasayati „to light" and OldSlav. *besiti (sę ) „to lead to madness, anger" (Serb-croat. bijes „a rage, fury", Pl.(z)biesić się - „to go mad" for example: about a wolf, which devoured a bies), *besьnъ „a madman", *besьnikъ „t.s." (in the sense OldPl. wiła (vila) „a madman" < wić się (viti sę ) "to snake" - maybe about movements doing by a medicine man during ritual bringing himself into the state of ecstasy, błazen „t. s., a fool" - compare OldChurchSlav. blazniti „to deceive, delude" - perhaps originally name of pagan priest).

The motive of profetic rage was important in IE. mythologies: Germ. Odhinn, Greek Dionysos, Apollo.