Perun is a Slavic God of sky, thunder and rain. Svarog was also considered as God of sky, however, Perun ruled over physical, atmospheric realm, while Svarog ruled over Prav - Realm of Gods and spirits of dead. As God who had the strongest cult, next to Dažbog and Svarog, Perun was considered the most powerful God in Slavic folklore. Historians, not even today know if He was chief God of all Slavs.
He is represented as muscular, bearded warrior whose weapon was axe, decorated with thunder marks and used in battle against Veles - His arch-enemy. While His tree was oak and flower was ''perunika'' (iris germanica). His another weapon was probably the weirdest one - golden apples. Whenever Perun tossed them into the air, they would transform into thunder. He rode burning chariot pulled by fiery-mane horses who breathed fire and sounds of thunder were actually sounds of His chariots.
Perun was tied to justice and order. He could punish evil people by closing the gates of Iriy (place in realm of Prav dedicated to virtuous people), or by striking them down with lightning bolts.
Battle between Perun and Veles
Because of His role of bringer of thunder and rain, all Slavs, no matter of tribe, paid Him a tribute in form of food or ''dodole dancing'' to battle the drought, especially during Summer season.
There is story that Veles, in form of horned serpent would slither His way to top of World Tree, causing Yav - human world to run dry. However, Perun would battle him with His axe and eventually kill Him, throwing Him down to the ground and announcing His victory by bringing rain and thunder. But Veles never dies and cycle of battle, death and rebirth is repeating every time before rain happens.
Though Perun and Veles are pretty much neutral in mentality, their battle is still considered as battle between order and chaos.