Nico, the son of Hades, and his boyfriend Will, the son of Apollo, travel to Tartarus, the deepest, darkest part of the Underworld as they attempt to rescue an old friend. As the son of Hades, Nico di Angelo has been through so much, from the premature deaths of his mother and sister, to being outed against his will, to losing his friend Jason during the trials of Apollo. But there is a ray of sunshine in his life-literally: his boyfriend, Will Solace,...

"The last kids may have escaped the forbidden fortress by the skin of their teeth, but there isn't much to celebrate. Thrull has what he needs to complete the Tower, Rezzoch will most certainly come to Earth, and the world as they know it will cease to exist. Except Jack's Cosmic Hand is now even more powerful than he realized, and it might just be able to stop the inevitable from happening. To get the answers he seeks, he'll need to travel farther...