Astonishing X-Men, Volume 2: Dangerous

A tragic death at the Xavier Institute reveals a powerful enemy living among the X-Men that they could never have suspected - and no, it's not Magneto. Things heat up in a way none of the X-Men ever dreamed, but will teamwork save the day when they can't even depend on themselves? Collects Astonishing X-Men (2004) #7-12