The X-Men: Watchers on the Walls — Christopher L. Bennett

In this X-Men adventure novel, an alien species seeking refuge on Earth pose an extinction-level threat to the planet. Hounded by a warship bent on its destruction, an alien spacecraft crashes to Earth. The X-Men race to the scene to help the aliens, but even though they come in peace, the beings onboard could cause mass death across the globe just by their presence. Now the X-Men face an impossible moral dilemma. These aliens deserve to be defended. But they are, by simple biological makeup, an enemy to life on Earth. Long persecuted for being born different, will the X-Men now protect the innocent—or join with their former foes to destroy an evolutionary menace?