On Earth-One, Daniel Patrick Cassidy was a stuntman who doubled as a special effects inventor. While filming a scene in his Blue Devil costume, he confronted an alien entity whose extra-dimensional energies merged Cassidy with his suit. Becoming a super powered individual, Daniel transformed a reluctant hero. He would ally with Justice Leaguers occasionally, and would eventually meet another version of himself as both traveled through outer space in stellar vessels.
On Earth-Two, Christopher Pike was an astronaut who while aboard the Vulcan Probe One during a two hundred day mission orbiting the sun went insane. Slaying his tw colleagues, during his rage Commander Pike damaged his vessel and nearly died when his module melted around him. An alien passerby named XLK-JNN used his advanced technology to transform Pike and the module into Vulcan Son of Fire. However, Vulcan returned to his native world and sought to sway his former heroes, the Justice Society. That team defeated Pike, sending him to Limbo until fellow interdimensional prisoners of the Secret Society of Super-Villains recruited him back to Earth-Two.
These colorful crusaders pretty much lived inside their superhumanly strong suits of armor, emitting pyrotechnic flames while wielding powerful staffs that unable them to fly through the air.
Blue Devil was joined by young sidekick Edward Bloomberg, who created his own uniform with gadgets as Kid Devil, Cassidy and Vulcan never had occasion to meet Bloomberg's counterpart, criminal arsonist the Flare who battled Little Boy Blue and the Blue Boys repeatedly.