Belobog

The white God of the waxing year; Guardian of the summer. Bailobog would defeat his brother in battle every Koliada to take his rightful place as the ruler of the waxing year. At Kupalo, Czarnobog would defeat Bailobog in battle to assume his position of ruler of the waning half of the year. Bailobog is said only to appear by day to assist travelers to find their way out of dark forests or reapers in the fields.

See also Polish_mythology