What is The Curse of Delos

The curse of delos is a flower that is found on the island where Apollo and Artemis are staying. The flowers are a result of the fact that Hera made a deal with the nature spirits to turn away Leto when she was getting ready to have Artemis and Apollo. The catch was that the agreement was for every 'land' that was rooted on the earth...but Delos was a floating island, and the spirits of nature welcomed Leto. Upset that she'd been uprooted, she made sure that Delos became rooted, and no longer an island. However, the island spirits were so honored to be the new sacred place for Apollo and Artemis (and Leto) that they covered the island in the flowers.

This flower, along with several other components, are what the demigods need in order to construct the Physician's Cure.