The Soul Harvester

From the introduction: Located in a deep mountain cavern, the Soul Harvester is a processing facility used to remove the souls from mortal beings and fill them with necrotic energy to create minions for the Demon Lord of Undead. Recently, reports of missing people from the surrounding area have increased. Just the other night the residents of an entire small town disappeared and tracks leading away from town lead up into the mountains and to the entrance to these caverns.