X-Men #39

Published in December 1967, X-Men #39 represents a transitional moment in the history of the original mutant series. By this stage in the Silver Age, the title was struggling to maintain the same commercial momentum as other Marvel properties like The Fantastic Four or The Amazing Spider-Man, leading the editorial team to lean into more experimental storytelling and dynamic visuals to retain their audience.

The issue features the artistic contributions of Don Heck, who brought a more grounded, illustrative style to the series, and writing by Roy Thomas, who was instrumental in fleshing out the interpersonal dynamics of the team. The cover and interior panels reflected the era's focus on individual character tension and the growing threat of global antagonists, a stylistic shift that sought to balance traditional superhero tropes with the increasingly complex character development that would later define the X-Men's resurgence.