The Swallowtail Festival is a major autumnal holiday that occurs on the first Fireday of the month of Rova. It is the most important holiday for the Church of Desna.
The holiday commemorates a legend about Desna. The legend says that after a terrible battle against the demon-goddessLamashtu, a badly wounded avatar of Desna fell to earth. A poor, blind child discovered the striken avatar, and nursed her back to health. To express her gratitude to the child, the goddess Desna transformed the child into an beautiful immortal swallowtail butterfly, so she could explore the wonders of the universe for all eternity.
To celebrate this event, the central ceremony of the Festival is the Swallowtail Release: A huge cage of swallowtail butterflies is released in front of believers. It is considered to be a very good omen if a butterfly lands on a believer for a short time. Larger temples of Desna often have large partially-enclosed gardens in which numbers of swallowtail butterflies are raised for the annual ceremony.
The day is traditionally celebrated with feasts, public performances of music and storytelling, and street fairs.