Arrun was a kingdom in the Special Region that collapsed about 500 years before the series began, or in the 100s Imperial Calendar, or the 1500s AD. Arrun was located in an area of semi-arid to arid climate near the edge of the deserts which stretch east of the Rho River. In the past, as humans wanted to gain immortality, Arrun had hunted down dark elves where the captured subjects had been imprisoned and experimented in a research facility; both the facility and the Labyrinth notably has many traps inside. The Arrun's research presumably ended in failure where the failed result was what later created the Crety Epidemic many years later. Aside from this, little is known about Arrun or the cause of its collapse, though it can be assumed that, after it's decline, that its lands were co-opted into the Empire. The only relic of Arrun to appear in the series thus far is the Arrun Labyrinth, near Crety. Around the time the JSDF first arrived in the area, the Labyrinth was abandoned, and used as a place to dispose of the bodies of victims of the Crety Epidemic before they reanimated. Thus, the place is filled with infected, in addition to dangerous animals such as cockatrices and minotaurs.