|Manga Debut||Chapter 16|
Acheron (アケロン, Akeron), also known as the "Prison of Demon Lords" (魔王の刑務所, Maō no Keimusho), is a magical penitentiary facility were some of the most dangerous evil wizards are kept.
The prison is located on a small island, in the middle of a body of water, occupying the entire rocky area.
- "Acheron" is a Greek river, that, in Japanese kanji, is translated as "三途の川" (Sanzunokawa; Literally meaning "River of the Three Routes"). In Greek mithology, the rivers Styx, Phlegethon, Acheron, and Cocytus all converge at the center of the underworld on a great marsh, which is also sometimes called the Styx.