In Celtic mythology, tales of the Tuatha Dé Danann reveal themes of fertility and eternal life, showcasing their connection to nature and the otherworld. They embody the ideal of a mystical society with advanced skills, such as magic and craftsmanship, elevating their legends in Celtic culture. The stories often emphasize the struggle against the Fomorians, symbolizing good vs. evil and the cycles of life and death. The balance between humans and the divine reflects ancient Celtic views on the intertwining of the material and spiritual realms, providing insights into their societal values.