Extraordinary X-Men (2015-2017) #5

The clock is winding down for mutantkind and one of the X-Men's oldest foes has come to speed up the process: Mister Sinister has returned! And he's bringing the X-Men face-to-face with their greatest fear. As the first chapter of Extraordinary X-Men races to its exciting conclusion, one thing's for sure for this team of all-new, all-different X-Men: not everyone will emerge unscathed.