After receiving a scroll, Twilight and her friends embark on an adventure into the depths of Tartarus to reseal the magical bonds that hold its creatures and convicts locked in. They meet the eccentric Hades and discover that they weren't formally invited and are forever trapped within the underworld. Conspiracy unfolds for the main six, as well as for the Ruler of Tartarus. Given a deal to complete their original mission, they have a chance to leave, but dark forces shadow their path as they journey through the depths of Tartarus.

"I hate to be informal, but… welcome to Hell."