Edom is a demon realm.
Edom is inhabited by the demons known as asmodei, among other demons.
At one point, Valentine Morgenstern sent his son Jonathan to Edom, where the boy was soon disfigured to fit their world. He spent many years there, enduring torture from demons, but also managed to spend time with his would-be mother figure Lilith. Jonathan was eventually able to escape with Azazel's help. When Jonathan died on Earth, he used his dying moments to open a rift to Edom and summoned Lilith, who sent through a horde of asmodei.