X-Men #10

Published in March 1965, X-Men #10 stands as a significant milestone in the early Silver Age of Marvel Comics. This issue was written by Stan Lee and features the illustrative work of Jack Kirby, with inks by Vince Colletta. It is primarily noted for the first appearance of the villain Ka-Zar, a character Marvel revived from pulp magazine origins, and features the X-Men venturing into the Savage Land, a hidden prehistoric jungle in Antarctica that would become a cornerstone setting for the franchise's lore.

The creative direction for X-Men #10 reflected the era's fascination with science fiction and 'lost world' tropes, blending them with the burgeoning mutant superhero narrative. At the time, the series was still establishing its identity and trying to capture a consistent audience among Marvel's rapidly growing reader base. While not as iconic as later runs that defined the team, the issue is remembered by collectors for its early expansion of the X-Men’s world beyond their Westchester school and for Kirby’s dynamic, sweeping depictions of the Savage Land.