"Aos sí" are seen as fierce guardians of their abodes—whether a fairy hill, a fairy ring, a special tree (often a hawthorn) or a particular loch or wood. It is believed that infringing on these spaces will cause the "aos sí" to retaliate in an effort to remove the people or objects that invaded their homes. Many of these tales contribute to the changeling myth in west European folklore, with the "aos sí" kidnapping trespassers or replacing their children with changelings as a punishment for transgressing. The "aos sí" are often connected to certain times of year and hours; as the Gaelic Otherworld is believed to come closer to the mortal world at the times of dusk and dawn, the "aos sí" correspondingly become easier to encounter. Some festivals such as Samhain, Beltane and Midsummer are also associated with the "aos sí."