Collects Astonishing X-Men #36, 37, 39 & 41. Not all monsters are easy to spot - and in the Marvel Universe, most of them live on Monster Island. Or, at least, they did. A mysterious exodus is under way; monsters spilling onto nearby shores - with catastrophic results - and it falls upon a small group of X-Men to both save the population from destruction and solve an imposing riddle: What are monsters afraid of?