Alecto's Osteoid Orchestra

An orchestra of ghostly skeletal musicians rise from below a 20-foot square on ground that you can see within range. For the duration, this orchestra turns this ground into difficult terrain, as the only way to progress through the orchestra is to join in their dance. While within the orchestra's square, creatures are effectively deafened. As a bonus action, you may move the orchestra up to 10 feet in a direction of your choice.

When a creature enters the affected area for the first time on a turn or starts its turn there, the creature takes 5d4 thunder damage.