As games evolve over time and new sequels are released, the need for change will naturally arise. In order to prevent a franchise from becoming stale in an ever-evolving market, a new title has to play around with the original formula, mechanics, and, of course, the story.
In some cases, the changes can do more than just build on the parts of the old game—they can completely replace them. In order to facilitate a new concept, the game developers might be forced to scrap some of the old ideas, and this may include the original game's story.
In some cases, these kinds of changes in canon can even extend to games working off other types of media like movies and books.
It's not hard to guess that drastic canon changes like this don't tend to go over well with the fans of a particular franchise. Although sometimes such changes might be necessary, they still go down as frustrating betrayals of their source material. Here are some video game sequels that didn't stay true to what was established.
10. Warlocks Are Legal Again - World Of Warcraft
World of Warcraft is known to constantly retcon minor details regarding its universe. Some retcons can even have a pretty major impact on the game's story and characters, like the complete change of Aegwynn's personality, for example. However, even changes like this seem minor when compared to what Blizzard had to do with the canon of the original Warcraft series in order to incorporate it into their MMORPG sequel.
The story of Warcraft III ended with Thrall banishing all warlocks from the Horde for their dealings with demons and their crimes during the war. Given what Gul'dan had done in the game and the fact that Orcs used to be enslaved by demons, this decision seems to be a logical conclusion to the story.
However, in World of Warcraft, warlocks are somehow returned to the Horde without any mention of their banishment.
This is obviously because the game included the warlock class in its roster, and not allowing one side to use it would make WoW less fun to play. Still, this change in lore seriously undermines Thrall's accomplishments in Warcraft III and creates a confusing gap in the story.