In Slavic mythology, the deity of the underworld is often referred to as Veles. Veles is associated with various attributes, including the earth, waters, and the underworld, acting as a protector of livestock and the harvest. He is in constant opposition to the sky god Perun, highlighting the duality in Slavic cosmology. Veles is also linked to magic and the mystical, representing a transition between life and death. His myths emphasize the importance of fertility and the cycles of nature in Slavic culture.