One of the most pivotal marketing strategies for Marvel was the construction of shared universe storytelling, and though X-Men was often its own isolated corner of the Marvel universe, Claremont’s work was deeply affected by and deeply affecting of this strategy. 1/7 #xmen

Claremont wrote the first DC/Marvel crossover, 1982’s “Uncanny X-Men and the New Teen Titans,” which DC comics historian Matthew K. Manning identifies as "one of the most well-received crossovers of its time - or of any time for that matter." 2/7

Marvel’s first line-wide crossover event was “Secret Wars” in 1984, an event that caused some notorious continuity complications for Claremont in the pages of X-Men, perhaps serving as an example of the challenges these events create. 3/7

Nonetheless, the first crossover for the X-Men line, specifically, was “Mutant Massacre” in 1986, devised and partially scripted by Claremont. The success of that event would create the annual tradition of X-Men crossovers, which still exists today. 4/7

Less formally, Claremont (like many Marvel writers) would frequently (and informally) intersect storylines between X-Men and other titles he was writing such as Iron Fist, Marvel Team-Up, Ms. Marvel, and Spider-Woman, to name just a few. 5/7

This was a good way to boost sales for a flagging series, but also became an important tool for implicating the broader marvel universe into that of the X-Men specifically, resulting in a number of iconic superheroes being pulled into the X-Men’s orbit. 6/7

Claremont plays an important role in the history of Marvel crossovers and, of course, Marvel crossovers had a deep impact on the run, showcasing both the scale and scope that such storytelling could provide, as well as the complications and challenges to narrative cohesion. 7/7