This weekend, we'll let our madness do the driving and see where it takes us.
"Madness has brought you here to me. I shall be your undoing!"
Prince Malchezaar is a prince of the Eredar and member of the Burning Legion, and final boss of Karazahn. Sometime after Medivh's death, Malchezaar took up residence in his old tower, Karazahn, and claimed it for himself. His true motives and goals remain unexplored, however as Karazahn sits atop a powerful convergence of magical ley lines, and can act as a bridge between Azeroth and the Nether, it shouldn't be surprising that a demon would want to claim possession of the tower. Vast magical power at your disposal, and free access to a world? What more would a demon want? Malchezaar is a noted collector of magic weapons, and has managed to claim several interesting pieces. Of particular note is Gorehowl.
The axe of Grom Hellscream has sown terror across hundreds of battlefields.
Gorehowl was the axe of Grom Hellscream, famously used by him to slay the demon Mannoroth, and a whole lot of other people. After his death, Thrall held onto the axe, eventually passing it on to Grom's son, Garrosh Hellscream. Garrosh then proceeded to use the axe to kill a lot of people, including Cairne Bloodhoof, until he discarded it in favour of Xal'atoh, a warped copy of Gorehowl, forged using the power of the Old God, Y'Shaarj.
The question that has plagued people since Burning Crusade has been how, exactly, did Gorehowl end up in Prince Malchezaar's loot table? It's possible (likely) that they just wanted to put a famous weapon in his loot table to show that he was a collector of weapons, and the axe of Grom Hellscream simply seemed like a good fit. Did Malchezaar somehow manage to steal Gorehowl after it was used to kill Mannoroth, and it remained in his possession until it was taken from him by adventurers who in turn gave to Thrall who passed it on to Garrosh? The latest expansion, however, opens up some far more interesting possibilities, as Warlords of Dreanor takes place in an alternate past version of the world of Draenor, in which the Burning Legion was not successful in transforming the orcs into their own, personal, crazed, bloodlusted and rampaging army. They're still conquers though. Either way, Warlords of Draenor has shown us that their are alternate versions of the worlds we know, and that they're places we can go to.
https://www.youtube.com/watch?v=2aRBL590Bd8
"All realities, all dimensions are open to me!"
Suddenly, what had seemed like a simple badass boast while calling an infernal down on our heads seems a lot more sinister. Alternate Draenor introduces us to an alternate Burning Legion. It seems possible that Prince Malchezaar is, in fact, a demon from another reality where he collected that world's Gorehowl, while our reality's Gorehowl remained in its chain of possession. Alternatively, with Karazahn already being a weird place and a portal to other worlds, its possible that we're the ones who wandered into Malchezaar's reality where he was master of Karazahn, while our Karazahn was actually just full of dust and ghosts.
Anyway, regardless of our or his origins, Prince Malchezaar was defeated by adventurers and banished from Karazahn. As a demon, it's unlikely that he was killed permanently, although as we did fight him within something like the Twisting Nether, so its possible that he may have been actually been killed. Fate: unknown.