This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages)(Learn how and when to remove this template message)
Errtu was featured as a villain of the first book in the Icewind Dale trilogy, The Crystal Shard by R. A. Salvatore, and the main villain of Passage to Dawn, the final book in Salvatore's Legacy of the Drow series. Second to the assassin Artemis Entreri and Obould Many-Arrows, Errtu is the greatest nemesis and most powerful and dangerous foe of the drow renegade, Drizzt Do'Urden, though Errtu has described himself as 'he who hates Drizzt most'.
Errtu is some twelve feet tall, covered in red scales, with a large pair of bat-like wings and a tail, and is frequently described as having a "horned, ape-like head" (Salvatore 2007) and a "canine maw" (Salvatore 2007). When he's in the throes of lust for power, he drools an acidic saliva. Errtu's voice is gravelly, guttural, and harsh. He is the ruler of a layer of the Abyss characterized by the growth of giant mushrooms, and even has a throne carved into the stalk of one. In battle, Errtu usually uses a many-tailed whip, a sword of lightning, and his considerable magic, wits, and demonic strength.
Errtu's motivations are primarily those of the average demon's — his own power, his own survival, and the chance to cause havoc in the Prime Material Plane. He is concerned entirely with himself and his own quest for power and control, and his selfishness leads him nearly to paranoia — in his view, anything that goes wrong is a conspiracy against him. Given Errtu's native environment, and the temperament of its denizens, this is an excellent survival trait and not too wide of the mark.
Despite that, Errtu is intelligent, and a capable tactician. The simple fact that, unless something greater destroys him in the Abyss (which is unlikely), he will exist almost for eternity, allows him to have considerable patience if it will be rewarded with a considerable increase in power.
He's also able to think laterally, and work around his problems. In Passage to Dawn, he released himself from a wizard's circle by using an anti-magic stone he kept in a bag, a leftover from the Time of Troubles. This dispelled the summoner's protective magic circle, which was otherwise flawless, and likewise disabled Errtu's magical abilities. However, Errtu, massive as he was, did not need them to kill the summoner.
He has been known to cooperate with other evil beings, gaining allies or even being them. In The Crystal Shard he chooses to ally himself with the wizard Akar Kessel, on the promise that when Kessel died (which would not be far in the future in Errtu's view, even if Kessel died of old age), he would gain Crenshinibon. In Siege of Darkness, he became a reluctant ally of the drow goddess Lolth — at first because she could obliterate him if he did not cooperate, and later because she offered him a chance to gain total, personal revenge on Drizzt. On a few occasions he offers subordinate posts to lesser demons to ensure their aid.
Like Artemis Entreri, Errtu holds an intense hatred of Drizzt Do'Urden, a drow outcast. Unlike Entreri, whose rivalry was based on pride and discovering who was the best, Errtu is motivated by sheer malevolence and revenge. Drizzt defeats Errtu twice in the course of his adventures.
The first time, when Errtu was serving as Akar Kessel's general, Drizzt summoned Errtu, to pose as a drow scout and inquire about Crenshinibon. When Errtu discovered Drizzt's ivory unicorn pendant, he attacked the drow, surrounding himself with flames and using his whip to catch Drizzt and pull him into the flames. Upon contact with Drizzt, the flames were extinguished—due to the magic of the as-yet unnamed scimitar Icingdeath. In a confused moment for both of them, Drizzt slashed Errtu with Icingdeath—causing the balor real pain and the blade's magic even freezing the tissues at the edge of the wound. Errtu was shocked—having never even heard of a weapon with that effect—and was stabbed in the stomach before he could recover. The scimitar's magic won out, destroying Errtu's material body and banishing him for a hundred years. As his body dissolved, Errtu reminded Drizzt of their long lifespans and promised revenge.
The second time proved much harder for Drizzt, as the balor had gained the artifact Crenshinibon, and had used it to build a stronghold in the Sea of Moving Ice, a body of water west of Icewind Dale and dotted with icebergs. Despite his dislike of cold, Errtu chose the place because of its natural barriers. He opened a gate to the Abyss and let innumerable lesser fiends through, as well as more powerful demons. Drizzt and his friends managed to fight their way through, and confronted Errtu in an ice cave. This time, Errtu had space to fly, and repeatedly teleported around the room, using his flames to melt nearby ice and fill the floor with water—in which he would periodically thrust his lightning-bladed sword to shock the companions. Drizzt and his friends would have died, if Wulfgar had not joined in the fight. Together, the companions managed to bring Errtu out of the air, where Drizzt could strike with Icingdeath.
In The Last Threshold, Errtu's time of banishment has expired. The imp Druzil tricks a wizard into summoning Errtu, and Errtu goes after Drizzt, damaging Ten-Towns. He is banished once more by the drow Tiago Baenre, who seeks to challenge Drizzt as Tiago's grandfather Dantrag did.
Errtu was the name of one of the original six Type VI demons in Gary Gygax's Advanced Dungeons and Dragons, its name being listed among the others in the appendices of the Dungeon Master Guide. As originally envisioned, there were only six Type VI Demons in existence, with each having its own individual name, unlike lesser demons (Types I through III and lower) which had only a species name (Type III being Glabrezu, for example.) The other five were Ndulu, Ter-Soth, Alzoll, Wendonai, and the greatest of all was named Balor. Both the description of the creature, with its fiery aura and sword and flaming whip, and the name "Balor" itself (taken from Irish mythology, see Balor) were intentionally reminiscent of the Balrog from The Lord of the Rings. Starting with Advanced Dungeons & Dragons 2nd Edition, in the Outer Planes Appendix of the Monster Compendium, the Type I - VI designation of demon types was dropped, and the name Balor was then used to refer to that entire breed of demon as a whole, and their numbers were increased dramatically from only six in existence to perhaps hundreds of thousands, and they were usually no longer given individual names in print, instead merely being referred to as "a Balor demon" or the like, and their individual significance was drastically reduced. As the novel in which Errtu was introduced as a character was written during the time of 1st Edition Advanced Dungeons & Dragons, Salvatore adhered to 1E AD&D conventions and chose one of the existing names to use for the demon.
At that time the novel was written, Errtu was one of the only six Type VI demons in existence, as opposed to being merely one of an innumerable horde of similar creatures which his type of demon became in later rule sets.