Why did skellig leave

Skellig was never meant to stay. They discover his wings, which indicate that he is an angel; however, Skellig never confirms this. He has a close connection to the owls and the spiritual world. The owls feed him, and he uses his newly gained strength to perform magic rituals with the children. Eventually, he revives Michael's sister and thanks the children for their kindness, leaving them feathers as a lucky charm.