Sandman

William Baker, better known as Flint Marko, was a small-time criminal who escaped from prison and stumbled onto a military atomic testing site on a beach in South Carolina, where a freak nuclear test bombardment fused his body with the surrounding sand at a molecular level. The accident granted him the ability to transform himself into living sand, and he soon clashed with Spider-Man as one of the wall-crawler's earliest and most persistent foes.

Few villains from Marvel's Silver Age have proven as enduringly fascinating as Sandman, who crashed onto the scene in The Amazing Spider-Man #4 in 1963, conjured by the legendary duo of Stan Lee and Steve Ditko. Over six-plus decades — spanning The Amazing Spider-Man, Fantastic Four, Ultimate Spider-Man, and well beyond — he has racked up an impressive 342 catalog appearances and 26 key issues, a testament to just how much storytelling weight this character carries. His affiliations tell their own rich story: he's run with both the villainous Frightful Four and the heroic Fantastic Four, making him one of Marvel's most morally complex recurring figures, sharing pages with titans like Spider-Man, Human Torch, Electro, and Otto Octavius along the way. If you're building a serious Marvel collection or simply want to trace the backbone of Silver Age storytelling, Sandman is absolutely essential reading.