Azhag the Slaughterer
Azhag the Slaughterer is one of the most famous orc warbosses in the history of Warhammer Fantasy, as he lead his massive WAAAAGH! of Orcs & Goblins to nearly defeat the empire, thanks to the wisdom and sorcerous might he gained due to wearing the haunted crown of Nagash.
Azhag the Slaughterer got this freaky piece of jewelry in his college years as a minor Warboss in Troll Country where, after having his ass handed to him by a bands of Chaos Warriors, he and his mob ran away into the ruins of Todtheim where, after fighting off a big-ass multi-headed troll found in its little treasure stash a fancy little crown. Which Azhag, in all of his orcish wisdom, put on his head.
Now, rather than most living being where, upon having a voice suddenly appear in your head saying "Hey bro! Want some help getting out of these ruins", they would throw said crown as far away as possible, all the time going "nope nope nope nope nope nuh-uh" Azhag just thought, "Sweet! Now there are two voices in my head!" and, following the Crown's directions, promptly waddled his demented green ass out of there.
From then on he continued to build up his warband, due to the general cracking heads and kicking ass tried and tested method used by all orcs. And so Azhag would have lived, WAAAAGHED and died happy and green. But then the Crown in all of its totally-not-evil-necromancer Nagash glory started going "Hey, have thought of using 'tactics'?" and, after explaining that they were not delightful little minty sweets, started to educate Azhag through calm and reasonable debate (see: Massive electric shocks and possession) that running screaming headfirst at the enemy was not a great idea.
And so, with battle tactics above that of a 5 year old and magical powers on behalf of Totally-not-Nagash-crown Azhag continued to kurb-stomp the entirety of the orc world, recruiting more orcs to his warband, to the point where he garnered so much respect that, from Red-eye night goblins, Azhag was given a MASSIVE WYVERN. You see, even "tamed" wyverns will spend 50% of their time trying to eat the warboss riding it and will spend the other 50% trying to throw him off, and you bet your ass that he is going to try to fly off the second the warboss gets off its slithery back. So imagine every orc and Goblin's surprise when Azhag walks up this this massive lizard, looks it dead in the eyes and (with a little help of not-Nagash-crown) immediately hops onto its back with the Wyvern suddenly as submissive and tame as a pet.
Eventually (whether this was the decision of Azhag or the Crown) Azhag decided to follow the paths of his ancestors and shouted to his massive Waaagh "OI BOYZ! OI RECKONS WE SHUD GO KRUMP DESE EMPIRE GITS!"
And that's what they did.
Now, the Empire was used to WAAAAGHs in the past, the simple fact that orcs had no plan past "Run screaming towards the guns Zulu style" meant that the orc hordes could be easily out-maneuvered and crushed. So imagine the Empire's surprise when on the field of battle, the Green savages didn't just charge like a bunch of screaming retards, face first into their front lines, and instead used a fairly complex strategies (courtesy of totally-not-Nagash-Crown) to utterly decimate the Empires armies.
Unfortunately Azhag's demented jewellery also ended up being his downfall as, despite having a tactical genius as a shiny headband, Azhag was still an orc and so often wanted to just "WAAAAGH WIV DA BOYZ" often to the dismay of the Crown, still, nothing that a good bit of electric shocks can't do! So Azhag's boyz were often confused as they saw their bit tough warboss pulling funny faces at random times as Azhag fought off mental attacks from the Crown screaming "STOP BEING SO RETARDED!". Unfortunately for Azhag, the Crown, like a attention seeking girlfriend, tended to act up at the worst times. And so, whilst in a particular scrap at the Battle of Ostland, Azhag flew his massive wyvern "Skullmuncha" into the middle of the fight to go krump some of the Knights Panther the Crown, seeing this as an utterly retarded move and so, trying to wrestle controls from Azhag, got into a complex mental battle with him, whilst fighting with fully trained knights. As you may expect, taking advantage of the orc warboss having a mental breakdown in the middle of a battle, the grandmaster of the Knights Panther quickly cut him down, causing Azhags waaagh to route from fear and lack of leadership.
After the Grand Theogonist saw the crown he demanded that the grandmaster of the Knights Panther hand it over. Despite thinking it would have made a pretty cool trophy, the grandmaster knew better and handed the crown over to the Grand Theogonist who promptly threw the Crown into the deepest vault in the Temple of Sigmar, where it waits to this day, twiddling its non-existent thumbs waiting for papa-Nagash to save it or just have some moron go "Ooh Shiny!"