Veles, also Volos, is among the best-attested of the Slavic gods, which sets him apart from many of the shadowy figures of that pantheon, and he is a god of cattle and wealth, of oaths, and of the world below. His importance is shown by his appearance in one of the oldest and most reliable of Slavic sources: the treaties concluded between the Rus and Byzantium in the tenth century, in which the Rus warriors swear to keep the peace by their weapons and by their gods, and the gods named are Perun, the thunder-god, and Volos, the cattle-god. To swear by Veles was thus a solemn and binding thing, and the pairing of Veles with Perun runs through the study of Slavic religion. Where Perun is the god of the storm, the sky and the warrior order, Veles is his counterpart below: a god associated with cattle and the wealth they represent (in an economy where livestock was wealth), with the underworld and the dead, with magic, and with the moist lowlands and waters, as against Perun's dry heights.
Some scholars, reconstructing from comparative Indo-European evidence and from the folk traditions in which the two are set against each other, have proposed an underlying myth of conflict between the thunder-god above and the serpentine cattle-and-underworld god below, Perun pursuing and striking Veles with his lightning, though the details of this reconstruction, like much in the field, are debated.
After the conversion some of Veles's associations appear to have passed to Christian figures, notably Saint Blaise, a patron of cattle. Veles stands as one of the few Slavic deities whose worship is directly and reliably documented, the god of the herds and their wealth, the witness of oaths, and the lord of the world below, set over against the thunderer of the bright sky.