Nilbogs are a type of monster in the Dungeons & Dragons role-playing game. They are a race of magical goblins that are healed by receiving damage and are damaged by healing spells. The name is "goblin" spelled backward, a reference to this reversal of effects. The exact connection between the nilbog and the llort, which shares its power to heal by receiving damage, is unknown.
Nilbog in other media
Nilbog is also the name of a fictional town in the film Troll 2. In this case it is also significant that the town's name is "goblin" spelled backwards, as the film, despite its title, features not trolls but goblins. Upon realizing the true meaning of the town's name, the film's protagonist Joshua becomes terrified, as he realizes Nilbog is the goblins' kingdom.
"Nilbog High" is also the name of the fictional high school at which you play in Career Mode of the video game Guitar Hero II.