Disney+ has released a trailer for Percy Jackson and the Olympians, the highly anticipated series based on Rick Riordan’s series of children’s fantasy novels.

The television show has been in the works for more than three years. It is an adaptation of Riordan’s book series, which kicked off in 2005 with The Lightning Thief; the sixth and latest installment, The Chalice of the Gods, is slated for publication next month by Hachette.

The novels follow the title character, a boy who discovers he’s a demigod and must help defend the world from the evil Titans. The first five books were huge bestsellers, and the first two were adapted into films that have since been bashed by Riordan.

The Disney+ series stars Walker Scobell as Percy, with other cast members including Leah Sava Jeffries, Aryan Simhadri, Jason Mantzoukas, Megan Mullally, Lin-Manuel Miranda, and Timothy Omundson. Riordan, who has voiced enthusiasm for the series, is among its executive producers.

The trailer features brief scenes from the series, with a voiceover saying, “The stories that I have told you about Greek gods and half-bloods—they are real.” At the end, there is a shot of Scobell, Jeffries, and Simhadri looking into the distance as a voice says, “Percy Jackson, we’ve been expecting you.”

Percy Jackson and the Olympians will premiere on Disney+ on Dec. 20.

Michael Schaub, a journalist and regular contributor to NPR, lives near Austin, Texas.