Moonstone

Karla Sofen is a brilliant but ruthless psychologist who manipulated her own patient, the original Moonstone, into surrendering a stolen Kree gravity stone, then absorbed the alien gem into her own body to gain powers of flight, phasing, and energy projection.

Few villains in Marvel's Bronze Age made an entrance quite like Moonstone — debuting in the pages of Captain America back in 1979, courtesy of a creative team that included Roger McKenzie, Roger Stern, and Sal Buscema, this character has been a fixture of Marvel's morally complicated corners ever since. With 132 catalog appearances spanning an impressive 46 years, Moonstone has proven far more than a one-arc antagonist, turning up most frequently in Thunderbolts, Captain America, and The Avengers — exactly the kind of company that signals a character with real staying power. Three key-issue appearances underscore their collector significance, and the roster of characters sharing those pages — Steve Rogers, Clint Barton, Songbird, Melissa Gold — reads like a who's who of Marvel's heroic and morally ambiguous alike. If you're drawn to characters who've haunted Marvel's best series across nearly five decades without ever quite settling into easy categories, Moonstone absolutely deserves a place on your pull list.