What are you trying to do here with this team, Marvel? They're supposed to be the problem kids of the X-universe, but they're far too small a class for all the psychotic mutants we have come across over the years. And while I understand including Havok so that readers have *some* classic good superhero to look to and root for, he really doesn't belong with this group. Like, at all. His worst sin is that he used to get possessed and/or mind-controlled a lot.
Some nice older X-villains make an appearance here. We already knew from previews that Madelyne Pryor would show up, so that's not really a spoiler. I enjoy how she points out that she came back years ago, "And nobody cared." Because her resurrection was so convoluted and confused after Changing Writers Syndrome took place in the pages of X-Man. At first she came back as a psychic ghost that X-Man manifested. Then it was declared that this origin was a lie, and she was actually an alternate reality version of Jean Grey, "Queen Jean" who came to invade. Then that explanation got kind of lost, and Madelyne Pryor showed up years ago with a bunch of female villains to rob Betsy Braddock's grave.
... No one referred to her as this alternate reality "Queen Jean," and no explanation was provided for how Madelyne came back from the dead if this were, in fact, meant to be Madelyne. Basically, if you were an actual long-term X-Men fan who just read the comics as they came out, there was no way this was ever going to make sense, because the writers made no attempt to reconcile the different explanations.
So, she's back. Some version of her.