Nihlathak

Nihlathak was an Elder of Harrogath who possessed the powers of a Necromancer. Though clearly not a follower of Rathma, like proper Necromancers, his status as an Elder may have allowed him to learn these skills for the purposes of performing final rites and communing with the Ancients.

Background
Nihlathak was the only Elder to survive when the elders gathered around the city of Harrogath to cast an ancient Druid spell of warding. After this, Nihlathak struck a deal with Baal, the Lord of Destruction. He would give Baal the Relic of the Ancients, the most holy totem of the people, so he could reach the summit of Mount Arreat without being challenged by the Ancients. In return, Baal would spare Harrogath.

Until the quest is completed, Nihlathak is found in the left-most corner of Harrogath. He has a very hostile personality, even to fellow s, and desires to keep to his own matters. It is revealed that it was he who kidnapped Anya and placed her in a Prison of Ice in the Crystalline Passage. He fled from Harrogath as Anya was close to being rescued.

After Anya is rescued, he is found in the Halls of Vaught as a super unique boss. He is defeated in the quest. He uses the most popular Necromancer Skills, Corpse Explosion along with and Summon Minion. To top everything off, he will try to freeze you using the Druid skill Arctic Blast. His Corpse Explosion was a sure one-hit killer in difficulty until it was nerfed in future patches.

In Hell difficulty, Nihlathak drops the Key of Destruction, which is a part of the Battle.net Pandemonium Event.

After completing the Prison of Ice
As the last surviving clan Elder, Nihlathak has been driven close to madness by his grief over the imminent failure of his clan to protect the Worldstone. Constantly ruminating on the myriad alternate courses the elders could have taken, he now lives with the guilt of not dying with his peers. Ultimately, he betrayed the world of Sanctuary by striking a deal with Baal.

Tips and Other Additional Information
Nihlathak's Corpse Explosion and Arctic Blast skills are the main reason he is feared among Hardcore players. When you kill one of his summoned Minions, make sure you use a skill that utilizes the corpse before Nihlathak can explode it such as the Paladin's Redemption, Barbarian's Find Potion, or Necromancer's Revive or Raise Skeleton. Equipping Items with the "Slain Monsters Rest in Peace" modifier such as the Nature's Peace Ring has the same effect. In and  you can also use freezing attacks to shatter the minions so they do not leave corpses. High Fire Resistance and Physical Damage Reduction/Block Rate will help against his Corpse Explosion. It is also possible to lure all enemies aside from Nihlathak far away from him before killing them making their bodies too far away for him to use as weapons against you. If you get too close, Nihlathak will use Arctic Blast on you, giving him greater advantage. Being frozen will put the players in greater danger. Having Thawing Potions, the cannot be frozen ability, or hit recovery will lessen the effects of Arctic Blast.

Skills

 * Summon Minion
 * Minion Frenzy
 * Corpse Explosion
 * Arctic Blast

Greetings

 * "What?"
 * "Hmmm?"
 * "Yes?"
 * "What is it?" (quick)
 * "What is it?" (slow)
 * "Be quick about it."
 * "Surprised to see you."

As an Enemy

 * "You have no idea of the power you face."
 * "I shall keep my end of Baal's bargain."
 * "For my homeland!"
 * "I will KILL you!"

Development
There is an unused aura graphic named "NehlithakGlow".

Also in the game files is an alternate Nihlathak's Death animation where his skeleton explodes instead of being dragged to the Burning Hells.

Trivia

 * His name is likely derived from the word nihil, meaning "nothing" in Latin.
 * He is one of at least two NPCs to become an enemy.
 * His death animation implies that he was indeed dragged into Hell to suffer for all eternity, as Anya scornfully remarks that he should.