Veles, also known as Volos (Russian: Волос, Влас, Власий), is a major Slavic god of earth, waters, livestock, and the underworld. His attributes are wet, wooly, hairy (bearded), dark and he is associated with cattle, the harvest, wealth, music, magic, and trickery.
According to reconstruction by some researchers, he is the opponent of the supreme thunder god Perun. As such he probably has been imagined as a dragon, which in the belief of the pagan Slavs is a chimeric being, a serpent that devours livestock. His tree is the willow much like Perun's tree is the oak.
Volos is mentioned as god of cattle and peasants, who will punish oath-breakers with diseases, the opposite of Perun who is described as a ruling god of war who punishes by death in battle.
According to Ivanov and Toporov, Veles' portrayal as having a penchant for mischief is evident both from his role in the storm myth and in carnival customs of Koledari shamans. In his role as a trickster god, he is in some ways similar to both Greek Hermes and Scandinavian Loki. He was connected with magic. The word volhov, obviously derived from his name, in some Slavic languages still means sorcerer while in the 12th century Ruthenian epic The Tale of Igor's Campaign, the character of Boyan the wizard is called Veles' grandson. Veles was also believed to be protector of travelling musicians. For instance, in some wedding ceremonies of northern Croatia (which continued up to the 20th century), the music would not start playing unless the bridegroom, when making a toast, spilled some of the wine on the ground, preferably over the roots of the nearest tree. The symbolism of this is clear, even though forgotten long ago by those still performing it: the musicians will not sing until a toast is made to their patron deity.
As a god of the underworld and dragons, he became identified with the Devil. His more benevolent sides were transformed to several Christian saints. As a protector of cattle, he became associated with Saint Blaise, popularly known among various Slavic nations as St. Vlaho, St. Blaz, or St. Vlasiy (Armenian: Սուրբ Վլասի; germ: Blasius; fr: Blaise; sp: San Blas; port: São Brás; it: San Biagio; Croat: sv. Blaž; eng: Blase; Greek: Άγιος Βλάσιος). In Yaroslavl, for example, the first church built on the site of Veles's pagan shrine was dedicated to St Blaise, for the latter's name was similar to Veles and he was likewise considered a heavenly patron of shepherds. As mentioned already, in many Eastern Slavic folk tales, he was replaced by St. Nicholas, probably because the popular stories of the saint describe him as a giver of wealth and a sort of a trickster.
The Russian philologists Vyacheslav Ivanov and Vladimir Toporov reconstructed the mythical battle of Perun and Veles through comparative study of various Indo-European mythologies and a large number of Slavic folk stories and songs. An unifying characteristic of all Indo-European mythologies is a story about a battle between a god of thunder and a huge serpent or a dragon. In the Slavic version of the myth, Perun is a god of thunder while Veles acts as a dragon who opposes him, consistent with the Vala etymology; he is also similar to the Etruscan underworld monster Vetha and to the dragon Illuyankas, enemy of the storm god of Hittite mythology.
The reason for the enmity between the two gods is Veles's theft of Perun's son, wife, or, usually, cattle. It is also an act of challenge: Veles, in the form of a huge serpent, slithers from the caves of the underworld and coils upwards the Slavic world tree towards Perun's heavenly domain. Perun retaliates and attacks Veles with his lightning bolts. Veles flees, hiding or transforming himself into trees, animals or people. In the end, he is killed by Perun and in this ritual death, whatever Veles stole is released from his battered body in the form of rain falling from the skies. This "storm myth", or "divine battle", as it is generally called by scholars today, explained to ancient Slavs the changing of seasons through the year. The dry periods were interpreted as the chaotic results of Veles' thievery. Storms and lightning were seen as divine battles. The ensuing rain was the triumph of Perun over Veles and the re-establishment of world order. On a deeper level, as has been said above, Perun's place is up, high and dry and Veles' down, low and wet. By climbing up into the sphere of Perun, Veles disrupts the equilibrium of the world and needs to be put in his place. Perun does this in a fierce battle by smiting him with his lightning and drives him down into the water under the tree stub and the log and by putting him back in his place Perun restores order. Then they stop being adversaries and remain just opponents until the next time Veles tries to crawl up into Perun's realm.
The myth was cyclical, repeating itself each year. The death of Veles was never permanent; he would reform himself as a serpent who would shed its old skin and would be reborn in a new body. Although in this particular myth he plays a negative role as bringer of chaos, Veles was not seen as an evil god by ancient Slavs. In fact, in many of the Russian folk tales, Veles, appearing under the Christian guise of St. Nicholas, saves the poor farmer and his cattle from the furious and destructive St. Elias the Thunderer, who represents Perun. The duality and conflict of Perun and Veles does not represent the dualistic clash of good and evil; rather, it is the opposition of the natural principles of earth and water (Veles) against heaven/sky and fire (Perun).