Der Tiefe

"In Der Tiefe, du bist einsam."

Der Tiefe is basically Hell, and should be treated as such. In Der Tiefe, there are fish that can fly, such as the Fische der Hohen, the top predator in the area. Only few have been to Der Tiefe and returned, as usually people get stuck. Evolution happened separately and basically backwards there, and therefore you get flying fish and underwater birds.