Mercury was probably resurrected off-screen at some point, given how Onslaught attached to people who were resurrected to manipulate them, and we saw...
Well...technically it's only 14 mutants going by what Hickman stipulated (13 if we count the F4 kid as no longer a mutant) with one or two mentioned...
This was a fantastic read. I'm usually very wary about anniversary issues because it's just a bunch of filler for more money but every story here was...