The various Celtic tribes were bound together by common speech, customs, and religion, rather than by any well-defined central governments. In Ireland, the Celts prospered, largely because the island was linguistically untouched for many centuries, and was islolated by the sea, making it inconvenient and inaccessible to Roman invaders.

The absence of political unity contributed substantially to the extinction of their way of life, making them vulnerable to their enemies. Their social power structure included warlords and priests known as druids. They lived in hill towns made to defend populated areas from other warring Celtic tribes. The nobles fought on foot with swords and spears and were fond of feasting and drinking. Celtic mythology, which included earth gods, various woodland spirits, and sun deities, was particularly rich in elfin demons and tutelaries, beings that still pervade the lore of peoples of Celtic ancestry.