Genbu Castle

About
The Genbu Castle is the a fortress built by Dark Lord Xavier's Apostle, Genbu. The castle has a blocking magic that locks those inside and makes so that it always must have at least one human being trapped within its walls. In order words, it's impossible to escape without leaving someone behind.

The castle is a special place trapped between dimensions where time does not pass, which means one could be trapped for eternity without aging. The dimension is unique and follows its own rules, which can make strange abnormalities like the conceiving of a human devil half-breed.