Ancient Germanic religion refers to the complex system of beliefs, practices, stories, and lore among the Germanic-speaking peoples before their conversion to Christianity. These ancient religious forms were intimately integrated into the Germanic culture and were influential in the formation of European civilization. Information about these ancient Germanic religions were first recorded by Julius Caesar in the 1st century B.C.E., but the origins of these religions are probably several millennia earlier. Their influence extended from the Black Sea all the way to Scandinavia and Greenland. The ancient indigenous Germanic religions are based on the worship and cults of a variety of gods, which are related not only to the cosmos, but also to nature. The details of these religions are best known through the lore and poetry of these cultures. These religions are polytheistic, but most claim that the gods can be divided into two tribes: Aesir and Vanir. According to tradition, these two gods fought but neither could attain victory, so a truce was accepted. Some of the more important gods include Odin (a shape-changing god foremost among the Aesir), Thor (a champion god particularly among the Saxons), Balder (a son of Odin and a favorite god among the Norse), and Frigg (the wife of Odin). Besides these gods, guardian spirits and dwarfs (who crafted the treasures of the gods) also played a significant role. Ancient Germanic rituals included animal sacrifice to the gods as well as festivals honoring the gods.