Ever heard of the game World of Warcraft? It’s a massive multiplayer online game, basically hundred of thousands people playing against each other in a huge fantasyworld. The developers, Blizzard Entertainment, decided to create a new boss which infected a plague on nearby players, the plague was intended to stay within controlled areas, but managed to escape and infecting almost every player on the server(s).
Often the best parts of a videogame are moments you don’t see coming, and sometimes the developers can’t even anticipate them! Personally, i think this is absolutely great. This is an element of gameplay that even if unintended, which might not be the case, can have far-reaching consequences.
Blizzard has already released a patch which cured the world, unfortunately, it was limited to the game-world only.