Arcanagos


 * For how to defeat his Undead Form found in Karazhan see Nightbane (tactics) and Nightbane (Return to Karazhan tactics).

Arcanagos was a powerful blue dragon who traveled to Karazhan just prior to the First War to confront Medivh, who unbeknownst to Arcanagos was possessed by Sargeras, lord of the Burning Legion.

Biography
When the Dark Portal was opened by Medivh, almost every creature attuned to magic on Azeroth felt ripples as the gateway flared to life. Arcanagos traveled to Karazhan with Medivh's mother, Aegwynn, to confront him about it. The tower was crowded with nobles who were expecting a gala, and so Aegwynn entered alone at first, hoping to convince Medivh to give up his power peacefully. After Medivh revealed that said power was that of Sargeras, he and Aegwynn began to fight, shaking the tower to its foundations and causing the would-be revelers to flee. When Aegwynn was temporarily incapacitated, Arcanagos joined in.

However, despite being a blue dragon, Arcanagos was severely outmatched. Sargeras struck him down, burning him from the inside out until all that was left was bone. Her friend's death sent Aegwynn further into a rage, and as their duel continued, Aegwynn slowly gained the upper hand.

The spell Medivh used against the dragon imparted some of his own essence into Arcanagos, imbuing him with fiery wrath. In order to divine information about Medivh, the Violet Eye has adventurers resurrect the dead dragon in order to extract the arcane essence. Arcanagos appears, now as a fiery skeletal monstrosity known as Nightbane, and proceeds to attack those who summon him.

Following the Fourth War, Mathias Shaw mentions in his reports that the agents he sent to meet the Shade of Medivh had seen Nightbane appear upon their arrival, at least, that's what their charred reports say.

Old lore
Arcanagos's story before Chronicle Volume 2 was told in the Nightbane quest chain:

Arcanagos sensed Medivh was being used by a dark and sinister force, and pleaded with him to abandon the tower before the situation escalated out of control. When Medivh refused to leave his residence, the blue dragon attempted to remove him by force. The two masters of the arcane fought briefly, trading blows, but the blue wyrm met his match in the corrupted Titan-imbued Guardian of Tirisfal. Burning from a horrific spell from the inside out, Arcanagos frantically flew off and crashed into the mountains of Deadwind Pass, dying a painful death, his bones shattering and falling down to scatter the surrounding area.

Encounter with Medivh

 * yell
 * yell
 * yell
 * yell
 * yell
 * yell
 * Arcanagos glows with a blue aura as Medivh casts a pyroblast that reflects off the dragon. Injured, Medivh stands back to his feet.
 * emote
 * Arcanagos begins to burn.
 * yell
 * Arcanagos flies off into the distance aflame.
 * say