Bondrewd

The infamous White Whistle who runs Ido Front.

Bondrewd, called Bondrewd the Novel, is a White Whistle of ill repute who commands Ido Front, a research station at the bottom of the fifth layer that guards the way into the sixth. He carries out horrifying experiments on children, including the one that turned Nanachi and Mitty into Hollows.

Background

He recruited orphans such as Nanachi with the promise that they would be trained as Cave Raiders. His adopted daughter Prushka has spent her whole life in the fifth layer, calls him Papa and befriends Riko.