Most ancient religions were polytheistic and possessed a respective pantheon of traditional deities, often enriched with figures from centuries of cultural encounters and experiences.
Today, most historical polytheistic religions are called mythology. In many cases, where the tradition was only taken orally, as in the case of the Celts, only names and few remarks in texts of neighboring cultures are preserved. Few religions of antiquity were not polytheistic. These include monotheistic Judaism and Christianity, dualistic Zoroastrianism and Mithraism.
In contrast, almost all the tribes and peoples of the early days had the idea that there were many gods and goddesses. Already a Sumerian list of gods from the first half of the 3rd millennium includes about 1000 names of gods, which represent above all different forces of nature.