The Thorn Hag, an ancient evil thought vanquished by the Elf Queen and her heroic companions many years ago, has arisen from the dead. A fey harp, created from the heart of the treant that perished in the battle, has gone missing from Satyrs' Glen and the Thorn Hag seems to be behind it. The PCs must track the missing harp through a warped and eerie wood and into an unseelie area of the Feywild to stop the Thorn Hag wreaking revenge upon the Elf Queen before it's too late - the clock is ticking. The Sylvan Harp is a D&D 5e adventure for 4-5 PCs of the 1st tier (Levels 1-4). The adventure has been designed with suitable alternatives to run the adventure for 1st, 2nd, 3rd or 4th-level characters, including advice for adapting creature numbers and/or powers to suit the level of your party. The adventure is estimated to take 8-12 hours to run. A timeline of events, and guidelines on how the actions of the PCs can affect those events, is included. The adventure includes nine new creatures: gwerthin, satyr bard, ash guardian, light guardian, treant spirit, pixie rot zombie, green dragon skeleton, thorn hag and thorn hag's hut. It also includes two new magical items: a powerful magical harp with a dark hidden secret and a crystal ball of clairvoyance. Also includes a player handout of the rhyming riddle of the fey, and maps of the area and a darkling tomb. Requires Volo's Guide to Monsters.