Equinox, the Thermodynamic Man, first appeared in Marvel Team-Up #23 (July 1974), and was created by Len Wein and Gil Kane.

Equinox is an African-American youth who gained superhuman powers due to accidental exposure to his father's malfunctioning equipment after a lab accident; his mother is Margay Sorenson, head of natural sciences at Bard College, while his father was killed in the same lab accident that gave Equinox his powers because he made a mistake.

[2] Equinox's powers were similar to the combined abilities of superheroes the Human Torch and Iceman, with whom he first battled,[3] as well as enhanced strength and durability.

His mother attempted to teach herself about her late husband's work to find a way to cure her son, but was ultimately forced to let Equinox commit robberies so she had the resources to carry out her research.

[5] Afterwards, Equinox joined Vil-Anon, a twelve-step program dedicated to helping individuals overcome their criminal tendencies.

[7] Equinox is next seen as a member of the Montana team of the Fifty State Initiative, Freedom Force, alongside Challenger, Cloud 9, Think Tank, and Spinner.

He froze Hardball, Ryder and Riot (of the Skrull Kill Krew) in ice and broke the glass over Think Tank's brain.

[13] Equinox returns in the All-New, All-Different Marvel when he is brainwashed by Kang the Conqueror's splintered half Mister Gryphon to attack the Avengers.