Hakkar the Houndmaster

Hakkar the Houndmaster is an agent of the Burning Legion and was the first major demon to cross the Well of Eternity portal. He supervised the portal's growth with Mannoroth during the War of the Ancients, and returned to create a powerful breed of mage-hunter felhounds during the third invasion of the Burning Legion.

War of the Ancients
Hakkar was one of the primary lieutenants of the Burning Legion. He was the first member of the Legion to set foot upon Azeroth and was described as a huge flaming, fleshless skeletal knight with a horned skull. He was sent through the portal created from the Well of Eternity to assist Xavius in strengthening the portal, preparing for the rest of the Burning Legion to come forth. Hakkar's primary weapon was a whip which could be used to summon a seemingly limitless supply of felhounds to do Hakkar's bidding. Hakkar attempted to remove Krasus and Malfurion from the resistance, but quick intervention by the Sisters of Elune saved the wayward pair. Hakkar was about to murder Tyrande when Malfurion Stormrage stepped in to prevent his love from being destroyed, calling down a fierce lightning storm to vanquish the Houndmaster.

Legion
Hakkar is one of the many demons summoned by in front of the Tomb of Sargeras to attack the forces of Azeroth in the climactic, disastrous battle for the Broken Shore where he remained for some time, being guarded by soulstalkers.

While on the trail of missing mages, Khadgar and a hunter adventurer find Hakkar in Suramar, where he intervenes before his felhounds can be stopped from feeding on the mages. Hakkar plans on feeding his hounds until they are strong enough to feed on every mage in Dalaran, and since Hakkar and his hounds are immune to most spells Khadgar asks the hunters of the Unseen Path to help. Hakkar's breeding grounds are on the island of Faronaar in Azsuna, where he breeds his hounds to be resistant to physical attacks just as much as magical ones. The Unseen Path travels there to capture one of the young beasts so that the warlock Kira Iresoul can examine it for weaknesses. The Unseen Path rallies the Silver Covenant, Farstriders, and Sentinels to set a trap for Hakkar and his powerful felhounds in the Violet Hold, and after defeating his favorite felhounds Kreenam and Czaadym send him back once again to the Twisting Nether.

Original timeline
In the original timeline, Hakkar survived the War of the Ancients and was killed during the Third War. When the Old Gods warped time and space in an effort to escape their prison, the timeline was altered in a variety of ways, among them Nozdormu's efforts to stop them, which in turn altered the course (though not the outcome) of the War of the Ancients. Hakkar's death at the hand of Malfurion Stormrage was one result of this, signifying that the old timeline was being overwritten, not relived.

Legacy
Hakkar's disciple, Omor the Unscarred, took charge his remaining felhounds after his death during the War of the Ancients.

War of the Ancients

 * "I am Hakkar... and you are nothing."

Houndmaster and Soulflayer
According to an interview with Richard A. Knaak, who wrote the War of the Ancients Trilogy, Hakkar the Houndmaster and Hakkar the Soulflayer are two different entities: ''Hakkar first existed in The Well of Eternity, as Hakkar the Houndmaster, my creation. Blizzard must have liked the name, because they accidentally took the name afterward for the troll god. Chris Metzen apologized for the mix-up at the L.A. Festival of Books.''

At BlizzCon 2005, Chris Metzen commented further:
 * "Essentially what happened is that in the War of the Ancients Trilogy, the first book, Richard had created a character named Hakkar. It was Hakkar the Houndmaster if memory serves. Pretty cool demon character, he's one of agents of the Burning Legion. And I think what happened, which happens more often than I really want to admit, it was such a cool name, which was jumbling around [my mind], when I went to jam out Hakkar the Soulflayer, "Hakkar, I'm a genius." <...> So, that was my bad."