stylistic:tone
Ancient proto-Indo-European religion

The head deity of the Proto-Indo-European religion was the god * Dyḗus Pḥ tḗr. A number of words derived from the name of this prominent deity are used in various Indo-European languages to denote a monotheistic God. Nonetheless, in spite of this, Proto-Indo-European religion itself was not monotheistic.

In Eastern Europe, the ancient traditions of the Slavic religion contained elements of monotheism. In the sixth century AD, the Byzantine chronicler Procopius recorded that the Slavs "acknowledge that one god, creator of lightning, is the only lord of all: to him do they sacrifice an ox and all sacrificial animals." The deity to whom Procopius is referring is the storm god Perún, whose name is derived from * Perk unos, the Proto-Indo-European god of lightning. The ancient Slavs syncretized him with the Germanic god Thor and the Biblical prophet Elijah.