Lightraider Challenge Part 1: The Castle of the Falls

From the introduction:

You have recently graduated from the LightRaider Academy and have left the town of Dayspring Highlands for a short trip. While on vacation you and your Academy friends are playing at the seashore. You have worked hard to earn graduation and are really enjoying the prospect of some carefree time on the sand and surf. But you are also eager for adventure and wonder if any can be found on these safe shores. You consider some of the possible exploits that await you far away when you are guided to step into one of the Passage Lakes and enter the Dragon Lands through a Hollow Tree.