Dark indeed.
Hyperbole be damned, the X-Men face their biggest threat ever in 135 issues plus one Annual. X-Men #135 is the issue when things go from dark to really dark. We realize that Jean is past the point of no return and doom is inevitable. Furthermore, we realize the scope of the Dark Phoenix in just four panels which show Spider-Man, Dr. Strange, Silver Surfer, and the Fantastic Four acknowledging the Phoenix Force. This is universe-impacting and that point is established in four panels instead of a company wide cross-over with variant covers and fluff-laden mini-series spin-offs.