Emperorshell

The Emperorshell is a creature living on the 6th layer of the Abyss, presumably first encountered by the White Whistle Delver Lyza, "The Annihilator", and having received its name from her.

Description
It is a lizard that appears to have adapted to the hazardous habitat of the Capital of the Unreturned, growing up in their eggshell and using it as a shield to keep them safe even from the "iron rain" of the 6th layer. They are quite ferocious, but edible, and can be eaten without too much preparation.

According to Lyza, they will continue to grow endlessly for as long as they live and they appear to have a ridiculously long lifespan. The legendary Delver claims to have encountered one with a towering frame of 30 meters. This Emperorshell was strong enough that even the White Whistle Delver Lyza, cherished for her phenomenal fighting ability, seemingly failed to take it down, leading to her naming it "Emperorshell" following her unsuccessful hunting.

Trivia

 * According to Lyza, the juvenile form of the Emperorshell is very tasty and whether or not the same goes for the one of enormous size she encountered too is a question she would leave for those who come after her to answer.
 * The habitat of the Emperorshells exceeds the depth of 14000 meters in the 6th layer and is accompanied by flaming rain.
 * The book that Nanachi used to read to Mitty contains a folk song apparently based on the White Whistles which bears a striking resemblance to the habitat of the Emberorshells the group encounters: "With time the boulders leave a trail becoming a hail of burning steel turning the ice-clad trees into clouds. Extending their necks through the skies the colossal turtles gather together to gaze at the amber sky."