Nico di Angelo, a son of Hades who has used the Death Trance.
A Death Trance is a trance that only children of Hades (and possibly also Pluto) can enter. The person must eat one of Persephone's pomegranate seeds in order to enter the Trance. One seed is equal to one day, during which a person who entered the Trance lies in a deathlike hibernation, consumes no oxygen and becomes very weak. It is unknown whether or not the user ages during the trance.
The Heroes of Olympus[]
The Mark of Athena[]
When captured by the Giants Otis and Ephialtes and trapped in a sealed bronze jar, Nico di Angelo enters this trance to stop himself from using up all his oxygen and dying. When Percy, Jason and Piper free him, he is said to be extremely weak and malnourished.
The Sun and the Star: A Nico di Angelo Adventure[]
Nico tells Will Solace and the troglodytes the story of how he got captured by the Gigantes, ending with Nico using pomegranate seeds given to him by Nemesis to put himself into a death trance in order to survive.