Thermo's parents were used in the forties for nuclear and cryogenic testing. As a consequence, Nathan Thurm inhereted a mutant gene which gave him the supernatural ability to control temperature.
As a teenager, Nathan attended Professor Xavier's school for mutants (see Marvel Comics). His powers were always overshadowed by the other mutants, and he eventually left that school.
Thermo is a founding member of AlertForce. Early in his career, he used his powers to create two incarnations: 'Ice Avenger,' for when he used his powers to create ice and cold, and 'Firefist,' for when he used his powers to create flame or heat. Although 'Ice Avenger' was an original member of AlertForce, he did not reveal his 'Firefist' persona until much later. In fact, for a time, many members of AlertForce believed that Firefist was a villain. (see issue #3).
Ice Avenger was the first team leader of AlertForce. However, he was very insecure about his powers and leadership abilities. This problem was compounded by the constant insubordination of team members Jack of All Trades and Knight Watchman. In time, Ice Avenger's confidence grew and he became a fair leader, but he eventualy turned over leadership of the team to Dreadnought, who was much better suited for the role. Thermo (as he became known later) eventually would become the team leader again, and was much better at it.
Thermo's primary nemesis during ERA I was the insane mutant called Fire&Ice. His powers were similar to Thermo's, which made him a strange foe. In addition, Thermo has had many battles with the lizard/man known as Slither. During one alien invasion, Thermo managed to convince Slither to join forces with AlertForce and battle the invading horde. To this day, Thermo is the only person to break through Slither's personality and achieve cooperation (although the villain Inventor did manage to place Slither under mental control to coerce Slither's participation in the villain group known as the Destroyers.)
During AlertForce's Mid-dity days (known as ERA I), Thermo fell in love with and married the mutant known as Flasher, who was also an AlertForce member at the time. Flasher was eventually killed by renegade agents of the FBI who were in league with the supervillain called The Inventor. Thermo hunted down and confronted the agents responsible, and was for a time hunted by the government. Years later, Thermo fell in love again, this time with millionaire heiress Mary Contrary (pronounced Contra - rie). The two were married at AlertForce mansion in Newark, New Jersey, and the function was attended by all manner of society hangers-on, as well as AlertForce and many other heroes.
Alas, however, marital bliss was not to be for Thermo. Soon after his second marriage, he was transported to an alternate dimension (along with Jack of All Trades and The Wall) during a battle with the Time Pirates (see rogues gallery). In the alternate timeline, Thermo's past was altered. He had never been known as Ice Avenger, had never been married to Flasher (who was known in this timeline as 'Copy' and was still alive, and was Thermo's mortal enemy), and had been divorced from Mary Contrary.
After the timeline conversion, Thermo changed his name permanently to 'Thermo,' abandoning the 'Ice Avenger' and 'Firefist' identities for good. He also changed his costume several times before settling on the 't'-angel logo he now wears.
Thermo has an obsession for the protection of genetic and other mutants. He takes whatever steps are necessary to further this goal, and he has constructed (and now runs) a boarding school in Alaska for the protection and training of young mutants (affectionately known by its students as 'Tundra Tech').
Throughout his life, Thermo has had many careers. Originally, he was Dreadnought's corner-man in a studio wrestling career. He later was a television pitchman for a very successful brand of Ice Cream (called 'Ice Avenger Ice Cream'). He has also been a reporter for the now-defunct Pittsburgh Press. He is currently affiliated with the Los Angeles Fire Department, and is working with a cosmetic company to endorse a cologne product called 'Fire&Ice' (which is ironic in light of Thermo's old nemesis of the same name).
After Dreadnoughts departure from the team, and Thermo's second stint as team leader, Thermo has loosened up considerably. He was traditionally very formal and serious, but now is able to relax and be more intuitive, both in his personal life and with his hero identity. He has lately taken to the habit of adopting various new costumes and identities when the mood and need suit him. He has been seen as 'The Weather Wizard,' 'Tommy the match boy,' not to mention his personal favorite, 'The Heat Mizer.'
What future adventures are in store for Thermo, only the gamemaster knows!
ERA V UPDATE:
After the 2001 reunion campaign, Thermo announced he was going into semi-retirement. He currently lives at his Alaska school for Mutants, and has intermittent contact with AlertForce. He has said he is available if some large crisis arises, but it remains to be seen whether Thermo will have future adventures with AlertForce.
2013 UPDATE:
After having founded and run the Flat Rock School for Gifted Mutants, Nathan Thurm succumbed to a longstanding medical condition and died in 2013.
