13 More Hardest Xbox One Achievements Of 2017

If there's one thing Call of Duty Zombies modes are known for, it's their extremely over the top and complicated easter eggs, and this year it's no different.

The achievement description for Dark Reunion is simply, "Save Klaus" which doesn't tell you much. You'll unlock it for completing the hard mode of zombies, which is the normal mode with a lot more bells and whistles.

There's no denying that this year's installment of zombies has to be one of the simplest and more linear versions to date, as the game will give you on screen instructions of what to do next. However, this only applies to the normal story progression of zombies, and once you deviate into the hard mode you're all on your own.

First, you're going to need to beat the zombies mode on normal to even go for this one. After all that's done, you're going to start up a fresh game and continue like normal until the last step, and that's when things get tricky. You're going to have to upgrade the Tesla Gun three different times, all of which are not a simple task and require you to kill specific zombies in specific parts of the map with specific traps. Then you'll need to find a bunch of random things littered across the map, of which will give you zero indication you can even interact with them.

That's just the "basic" rundown. The entire easter egg is far too complicated, with far too many little nuances to get into here. Even with its difficulty, this achievement is up there with Cuphead on unlock percentage , sitting at 0.37%. Obviously you're going to need to be a hell of a Zombies fan to unlock this one.