"The Dreaded Diablo!"
The Fantastic Four vacation in Transylvania but something goes wrong when Ben frees a feared alchemist who promises to help Ben revert from being the Thing.
The FF confront Ben, but he is staying with the alchemist, Diablo. Soon Diablo has most of the richest people in the world working for him with the promise of an immortality serum that Diablo has created.
But Diablo's potions only last for a short time, as he uses it to secure power but the FF move in and take Diablo down and Ben seals him back in his crypt.
First Appearance of Diablo.