One of the more durable villains in the Marvel Universe was the Wizard. He first appeared in Strange Tales #102, where we learn that he's fabulously wealthy from the inventions he's created, that he's a master chess player, and an accomplished magician. But as with many villains he longs for a challenge:
He creates a situation where only the Torch can rescue him, and in apparent gratitude, invites Johnny to his home. But once there he uses a water cannon to douse the Torch's flame, then imprisons him in an asbestos-lined room. Then he commits a series of crimes while disguised to look like the Torch. Johnny manages to get away, but he is apparently stymied when the Wizard shows him photographs revealing that the Wizard was actually behind the crime wave. But Sue helps out her brother by stealing the photos, thus clearing him.
This is something of an oddball story in that the Wizard is apparently well known by that name (indeed, we do not hear his real name in this story), but nobody supposedly knows the Torch's real identity, which was never hidden in the Fantastic Four series.
The Wizard returns in Strange Tales #105. After breaking free of prison, he resolves:
This is the sort of feedback loop that commonly exists between villains and heroes; hero defeats villain, villain must get revenge. It's extraordinarily common in the Marvel superhero mags of the 1960s and allows the writer to quickly set the stage for the inevitable battle.
The Torch and the Wizard battle it out for a few pages, before Johnny's sister, Sue Storm, arrives. After trapping her, the Wizard forces the Torch to join her, where a peril awaits:
These kinds of deathtraps became something of a cliche in the 1960s, even forming the centerpiece of the Batman TV series. At any rate, Johnny manages to disarm the trap and capture the Wizard.
The Wizard's next appearance is indeed a key story, as he teams up with Paste-Pot Pete, another villain from the Torch's rogues' gallery. This pair (with Pete renamed the Trapster) would later join up with the Sandman and Medusa (of the Inhumans) to become the Frightful Four, whom I discussed previously.
However, as in all such teamups the bickering between the two villains is intense:
The Wizard has a cameo appearance in two panels of Strange Tales #112, then returns for real in ST #118. This time he has invented an antigravity device which allows him to fly:
This invention became a staple of the Wizard's, appearing in many stories and giving rise to his more alliterative nickname, the Wingless Wizard.
After that, the Wizard mostly appeared in Fantastic Four issues, starting with the original Frightful Four appearance in FF #36.