Thunderbolt (Yz) first appeared in Flash Comics #1, published with a cover date of January 1940, and was created by John Wentworth and Stan Aschmeier.

[1][2][3] Yz is a fifth-dimensional genie who resided in a pen that was entrusted to Johnny Thunder on his birthday where the Badhnesians would use it to rule the world.

[9] In the DC Rebirth reboot, it was mentioned that Johnny Thunder lost Thunderbolt after Joseph McCarthy had him reveal his secret.

[10] In Doomsday Clock, Thunderbolt returned when Doctor Manhattan undid the experiment that erased the Justice Society of America and the Legion of Super-Heroes.

After Elias' defeat, Djinn restores Johnny Thunderbolt and leaves with Jakeem to explore her newfound freedom.