Errtu is a Balor, a true tanar'ri (chaotic evil demons) in the Dungeons & Dragons Forgotten Realms campaign setting, created by R. A. Salvatore to make his first appearance in Salvatore's first published work, The Crystal Shard . Second to the assassin Artemis Entreri, Errtu is the greatest nemesis and most powerful and dangerous foe of everyone's favorite drow renegade, Drizzt Do'Urden.

In The Crystal Shard, Errtu is summoned by an impertinent mage to the Prime Material Plane (our world, or Abeir-Toril; more specifically, Faerûn) and promptly destroys the conjurer and seeks the Crystal Shard; Crenshinibon , as it is called, the ancient and evil artifact he has been seeking for centuries. It currently lies in the possession of a wizard named Akar Kessell , and the fiend allies himself with the wizard to get closer to the artifact. He is banished to the Abyss for a hundred years when Drizzt Do'Urden "kills" him, destroying his physical body. Drizzt would have been killed by Errtu's flaming body, but, although he did not know it at that time, his magical scimitar, Icingdeath, protects its wielder from fire.

He makes a second appearance in Passage to Dawn , the final book in Salvatore's Legacy of the Drow series.