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WarCraft aka: Worldof Warcraft
In Warcraft III, Arthas's journey to evil was caused by his lust for vengeance against the demon Mal'Ganis and fulfilled by his willingness to sacrifice the life of Muradin Bronzebeard, a dwarf friend. However, in World of Warcraft, we discover that both of these characters are alive, absolutely wrecking the story both narratively and dramatically. This is completed with Muradin having amnesia, a second such case on a hero within a year. Then Blizzard gives us massive retcon in the new Rise of the Lich King novel, in which it is revealed that Arthas defeated Ner'zhul in the 'battle' for his mind... despite the fact that the entire point of the Undead campaign in Frozen Throne was about Arthas availing his body for Ner'zhul's use, and Blizzard's previous position was that Arthas and Ner'zhul had fused and the latter was in control of the Lich King's thought patterns.
Speaking of Rise of the Lich King, in it we also learn what tragic event gradually changed Arthas from an intelligent, good-natured boy into an arrogant zealot willing to butcher entire cities and sacrifice his friends to kill Mal'Ganis: his horse died. For bonus Narm, the first thing he did after seizing Lordaeron? He rezzed it.
Malygos, the dragon aspect of magic, went absolutely insane when his kin were killed by demons ten thousand years ago. In World of Warcraft, he comes to his senses, and the first thing he decides to do is kill all magic-users in the world to make sure the Burning Legion won't invade anymore. All this despite the fact that the mortal races already handed the Legion's ass to them twice in the first expansion set and magic-users being vital to the battle against all world-threatening evils, such as the Scourge, which lives in Malygos' neighbourhood and uses demon magic all the time. What is more, one of his solutions for solving the whole magic problem is tying the lay-lines of Azeroth to his home, thus preventing anyone outside it from touching the Arcane. The bad news? Tampering with the lay-lines has a big chance of causing an eco-catastrophe which can end all life on the planet. Fans were sure as hell that Malygos was being manipulated by some evil force, but seems Blizzard considers this good character development. It's not.
Also related to Malygos, during one of the quest chains in Coldarra, you lure him out in the open. The Red Dragonflight, led by the most powerful Aspect, the Dragonqueen Alexstrasza, put you on this chain. Now, any dragon with half a brain would have Alexstrasza ready and waiting to kick Malygos' tail across Northrend, but instead, they just have a bunch of smaller dragons flying around spitting fireballs at him. This, obviously, does not end well.
Alexstrasza herself didn't order the attack, Keristrasza did, and the Red Dragons participating in the attack were the ones already stationed around Coldarra. Keri took it upon herself to be stupid because she wanted revenge.
Zul'jin'sdefilement in patch 2.3. Ever since Warcraft III Horde trolls have been saying "Vengeance for Zul'jin". For most of Vanilla WoW it was said Zul'jin was a Messiah and hero for trolls everywhere. with both jungle and forest trolls allied with the Horde praising him and saying he would someday return to lead them to glory. Then comes patch 2.3 comes along and Zul'jin returns...... as an evil raid-boss in a rip-off of Zul'grub with the lame explanation "he was evil all along". Numerous instances of research failure make it all the worse, for example Zul'jin having a Jamaican accent and not regrowing his arm after it was cut off (Trolls having an innate Healing Factor). There isn't a good lore reason for killing him, the players are simply asked to do it by an unfunny redneck searching for treasure. The final kicker is that player trolls still yell "For Zul'jin" and a new troll hero to replace Zul'jin has yet to introduced. What a sad end to such an awesome character.
Many also saw the Shatterspear Trolls (dancing troll village)'s treatment in Cataclysm as basically pisstaking a perfectly useful set of NPC's. They started out as mysterious and cool, because it was rather difficult to get into their village and everybody wondered what was up with them. Come Cataclysm, Trolls can now be Druids, and since the Shatterspears are right next to Moonglade, many speculated they would join the Horde and teach the Darkspears the ways of druidism. Instead, they're used as mooks to get killed by new Night Elf players.
It also flies in the face of what Word of God said about them anyway. They said that the Shatterspears weren't interested in gaining any more land than they already had. In Cataclysm, they apparently just changed their mind for no reason and decided to try and take away the Night Elf land. And by Night Elf land, I mean some of the most populated Night Elf land in the whole world.
This may be one of the worst examples of a character or faction changing alignment for a stupid reason because they didn't even give that much. There is no explanation for why they suddenly changed their minds. The closest thing is a line in a "go kill some Shatterspear" quest text that could more or less be summed up as "the Cataclysm made the trolls angry."
Kael'thas, the ultimate Big Bad of the Burning Crusade era instance Tempest Keep effectively hands you the means to defeat him. First he sends four minibosses, one by one, then he sends floating mystical weapons, then he resurrects all four minibosses and you have to fight them all at once, then you fight him through two or three more phases. Those floating mystic weapons, once defeated, can and in fact must be picked up and equipped by every single player in the raid (each weapon 'corpse' yields theoretically infinite duplicates, each player can hold one and only one of each, there's a caster staff, a dps axe and dagger, a bow, a sword, shield and a healer mace). Each weapon carries buffs, many of them area-effect, that specifically target and cancel out extremely dangerous effects of the Miniboss Rush and Kael's subsequent phases - several of them basically being full wipes. If he did not manifest and send these weapons after player parties, those parties could not possibly succeed against him. This is either massive hubris or total Idiot Ball, but good lord, Kael, weren't you supposed to be smart?
Considering the utter and total Character Derailment he underwent between WCIII and WoW, this troper is not shocked at the addition of insult to injury. See also: the transformation of Illidan into a ginormous dickaroo, and attempted handwavings of Maiev being extremely insane.
Same can be said for many other bosses. Why in the world would Razuvius just keep two Mind Control Orbs in his room so you can mind control his students? Why does Faerlina keep these Adepts in the room while they don't do much and can dispell her Frenzy? More generally, most of the bosses are able to go Berzerk if you spend too much time killing them: why won't they just do it on the spot and wipe the floor with the raid group, instead of giving you a fair fight? Why can't they just go for the one in a dress?
Most of those are Gameplay and Story Segregation. Removing those mechanics might make more sense in the story, but it would make pretty much every boss in the game either really boring or far too easy, or both.
Being entirely fair to Blizzard, many of their heroes from Warcraft III onward have tended to grab hold of the Idiot Ball rather aggressively. Have we forgotten Tyrande of the Night Elves who spends an entire level slaughtering her own allies, half to rescue Illidian and half to spite Malfurion? Or even Medivh and his plan to warn the world by giving highly vague commands to the notoriously suspicious humans? Really this sort of stuff isn't particularly new.
You're all also forgetting the whole "Eredar corrupting Sargeras" thing getting changed around to "Sargeras corrupting the Eredar". In the original lore, the Eredar were the ones that corrupted Sargeras when he discovered their race. Now, with the lore retcon, Sargeras was the one that corrupted THEM. That led to a massive Wall Banger for this Troper who's been foaming at the mouth for the past several years as the lore of Warcraft, lore which she's LOVED since she got into it, has started getting screwed up thanks to how Blizzard has been handling their characters. At least Metzen manned up and admitted that was his mistake.
The Legion was told to corrupt races across the multiverse, most races just fell under the influence its influence... except the Eredar and the Nathrezim, whose actions directly resulted in Sargeras' Face-Heel Turn. In the original story, they are not mere servants of the God Of Evil, they are the former mortals whose actions resulted in The Paragonbreaking down and turning into the Bigger Bad. This troper believes it makes Archimonde and the Eredar much more interesting as villains. They are way under Sargeras in the Sorting Algorithm of Evil, yet they are more than The Remnant. Note that in the case of the orcs' corruption, the demons acted as The Man Behind the Man, with the orcs genuinely unaware that their lust for conquest was unnatural. It was more of a massiveRevision than a Rewrite.
"The Culling of Stratholme", namely, the behavior of Uther and Jaina. This episode is supposed to be the Moral Event Horizon for Arthas, but the effect is severely undermined, because he's actually right, there's no way to single out Zombie Infectees, and to slaughter the whole population is the only way to quell the plague. All the more jarring is Uther and Jaina' reaction that basically sums up to: "This is bad, mmkay?" without offering any alternative solutions. And you'd think that a paladin, of all people, would be the first person to stop someone from doing something they perceive as evil, but nope. Uther just yells at Arthas, then sits back and watches him do it.
It's more a case of doing the right thing for all the wrong reasons. The game gives plenty of reason to believe this is the case, given both Arthas' petulance when talking with Uther, and his obsessive pursuit of Mal'Ganis subsequently. That said, it is more than odd that neither Uther nor Jaina try to stop him, or do things another way.
This troper had similar concerns with Uther's reaction at first- then Fridge Logic hit. How WOULD Uther have stopped him, save interfering with the orders of the crown prince - aka, committing treason?
Uther is a Knight of the Silver Hand, a knightly order of Azeroth... or as it was later known, Stormwind, and before that he was apprenticed to Alonsus Faol, High Cleric of Northshire. Arthas is the crown prince of Lordaeron. Sure, Arthas's regular troops are surely oathbound to Lordaeron, but Uther is not.
Garrosh Hellscream in fucking general. Oh, you're building him up as a legitimate counterpoint to Thrall, being an ax-crazy idiotic bastard that is going to drive the Horde to the brink of war and back to everything that ruined them? Oh, that's OK. That's kinda cool, it serves as a plot to lead in the lore newbies to realize that orcs aren't necessarily "bad." The orcs will overthrow him and...wait, why are you suddenly making him noble to Thrall, whom he previously disrespected, out of nowhere, with no lead in? Why is he suddenly a brilliant tactician? Why is everyone around him praising the shit out of him, even though the vast majority of the player base hates him? Why is Thrall appointing him for the hamfisted reason of "well, the Horde can't bow to humans or something!" when there's much better candidates like Cairne (deceased because of Garrosh) and Vol'jin sitting right there? Oh, because they're old or some bullshit. Garrosh exists basically to market a dumb, fantasy stereotype-friendly Warcraft to pre-teens because it sells better to Black Ops playing console-tards than fantasy races that are somewhat nuanced and break basic conventions. "War back in Warcraft" my ass.
Thrall attempts to justify this to Vol'jin by saying the horde needs a strong leader who follows war-based orcish ways instead of the peaceful ways he was seeking to make it stronger. Yeah, right, with Garrosh leading blind, strategyless charges, Sylvanas starting (and on the losing end) of a war with Gilneas, Cairne's death and Baine only staying in the horde because his people need them, and the Trolls knowing exactly where Garrosh is taking them and second-guessing their alliance, the horde's never been weaker or more divided.
In Mists Of Pandaria, Garrosh undergoes a Face-Heel Turn, but basically the entire orcish race goes with him. The only orc characters to be in a positive light are Eitrigg, Thrall, and Saurfang, talk about unexplained Sudden Heel Syndrome and Aesop Amnesia.
Uldum was once a land shrouded in mystery. They'd been teasing it ever since vanilla, and the entrance just stood there, inaccessible, that whole time. So when they finally open it up, you expect it to be deeply involved in the lore and storylines of most of the game, and we might actually find some stuff out about the Titans. What we got instead was a long parody of an Indiana Jones movie, most of it is Played for Laughs. To make matters worse in this, your character is effectively made useless for much of the zone's storyline, forcing you to be rescued over and over again by the Indy Expy.
Two words: Goblin Hitler.
The model designs for the Night Elf archer and huntress units, along with the design for the dark ranger hero neutral hero unit (as well as campaign-only units like Sylvanas and the High Elven archers). To wit, these warriors all feel no need to protect their cleavage, their midriffs, portions of their lower back, and/or their legs from enemy weapons. These character models aren't comparable to the demon hunter or blademaster heroes, or the trolls and tauren units, since those models aren't making the pretense of wearing armor. The dark ranger, the archers, and the huntresses all have visual cues that suggest they should be properly protected. The dark ranger has shoulder armor and sturdy-looking boots with knee guards; the Night Elf archers have shoulder armor as well as thick boots and wrist guards; and the huntresses have armor that protects their legs and torsos along with helmets. All those features imply the ability to conceal vital parts of the body behind proper armor, which makes the refusal to do so jarring. The orc grunts suffer from this as well, with armor that only protects one side of the front part of their bodies, but whereas the grunts simply look crudely armored, the dark ranger, archers and huntresses look designed explicitly for Fanservice.
The last straw for this troper was a particular quest line involving the birth of Wrathion, the only pure member of the Black Dragonflight. While the goal of redeeming them is an admirable effort, they do so by at one point kidnapping and hiding a black dragoness and forcing her to produce eggs, then sending the player in to beat her into submission and take the eggs. Sound familiar? Of course it's done by the good guys and they are successful, so the moral of the story is rape is okay as long as it's on a monster and it's for a good cause.
What. The. Absolute. HELL. were they thinking giving Garrosh over to Taran Zhu of all people? He even has the audacity to claim that the Pandaren were affected the most by the war? They aren't even in the top 5. Millions of humans were killed, an entire people were nearly wiped out thanks to Garrosh's mana bomb. In case anyone forgot, the population of Theramoore contains every single remaining man woman or child of Lordaeron. Just about all of them died. And Taran Zhu wants to compare getting a bit of glowy Old God residue to NEAR GENOCIDE? They should have just had him die when Garrosh killed him.
I think this was Blizzard's attempt at a compromise, since before the cinematic was released there were lots of arguments over which faction deserved the canon kill more. Giving it to one side would have upset the other, and leaving it ambiguous could cause problems if Garrosh's death is referenced in future events, so they let a neutral faction deal with him. Sure, Taran Zhu made an arse of himself, but he always does that.
And to add to this controversity, some argue that this was a way to give Garrosh a Fate Worse than Death considering his obcession with his lifestyle of "Victory or Death" since it is more lilkey that the Pandaren will imprison him instead, robbing him of a glorious death in battle. Then again, it doesn't excuse the fact that the people of the Horde or the Alliance has no say in the upcomming trial, considering that they both suffered alot during the rule of Garrosh.
It gets worse. With the announcement of Warlords of Draenor, we find out that Garrosh not only escapes from Taran Zhu, manages to create the powerful Iron Horde from the uncorrupted orcish clans of an alternate timeline's Draenor (specifically the ones that would've been corrupted and gone to war with the Alliance in Warcraft I & II, had Garrosh not changed the timeline). To put this in perspective, not only did he Karma Houdini his way out of his trial, he's now again in a position of power where he can attempt conquer Azeroth. AGAIN. You really screwed the pooch on this one, Taran.
Thematically, the worst thing about handing Garrosh over to Taran Zhu is that Taran (like Garrosh himself) never learned the big lesson they shoved down our throats at the beginning of the Orgrimmar raid. Dude needs to spend some time with some shepherds.