For over ten thousand years, the Stearns have been Mr. Monsters, transferring the title from father to son. The Mr. Monster lineage is guarded by the Fluorescent Five, who act as spiritual teachers and provide the Mr. Monsters with their predecessors' knowledge. This knowledge enables them to quickly adapt to their role and learn from their predecessors' mistakes.
Created circa 1947 by Fred Kelly, the character was influenced by Kelly's earlier creation, also called Doc Stearne.
Jim Stearn is the son of the Depression Era Mr. Monster, who had been killed when Jim was ten. Jim was adopted by his father's friend Lionel Strongfort, who raised young Jim. While his father had been hard, even cruel, Lionel was a gentle man. Jim adored his adopted father. Believing that his father was killed because he was Mr. Monster, Jim initially refused to become Mr. Monster. Leaving his family's headquarters, Stearn Mansion and moved to Canada. He changed his name from 'Stearn' to 'Stearne' to distantiate himself from his family. Jim soon became a doctor. After placing an ad for an assistent, the ad was answered by Gloria Greene. The two fell in love instantly.
Investigating the case of a woman who was placed in a death-like trance by her husband, Jim Stearne stumbled upon a book on lycanthropy. Realizing this was his goal, he dedicated his life tracking down monsters. For the next few months, Jim traveled the darkest corners of the world to learn its secrets. Soon he designed himself a costume, finally becoming the World War II Mr. Monster.
After Mr. Monster barely defeated the "Terror of Trezma", Gloria Greene decided she couldn't live in fear anymore, always dreading for the day Mr. Monster was killed himself. She met detective Joe Friday after the battle and the two became enamored. Jim took the news in a hard way. Wandering America, he was one day approached by a little girl for help because her mother was attacked by a monster. The monster proved too strong for Jim. Fortunately, two cops, who were also alarmed by the little girl, shot the monster, which fled the scene.
While hospitalized, Jim met Lillith Weiss. She was secretly a vampire who liked the sun. She was part of a plot forged by the Vortex (a cabal of demons) to break the lineage of Mr. Monsters by not letting Jim have a son. She seduced him and eventually persuaded him to quit being Mr. Monster. Afraid of losing another loved one, he agreed. Lillith spoiled Jim with everything he liked to eat, making him fat and thus unable to be Mr. Monster.
She told Jim she was sterile, believing a human and a vampire can't reproduce. Nonetheless, after several years Lillith became pregnant. Their son came three months early and was born with his umbilical cord already severed. Jim and Lillith named their son Strongfort, after Jim's adopted father. Jim noticed that Lillith didn't take to Strongfort. She acted cold when Strongfort was around. As a result of the tension, Jim spent more and more time at the hospital and less time at home.
Planning to stop Strongfort from becoming Mister Monster, the then vampire king Mose sent Lillith a letter, ordering her to take Strongfort to Stearn Mansion, his father's former headquarters, and kill him there. When Jim came home, he found the letter. After recovering from the shock of being married to a vampire who was out to kill his son, Jim decided he needed to become Mr. Monster again to save his son. However, vampires set his house on fire, trapping Jim inside. Contacted by the Fluorescent Five, Jim agreed to become Mr. Monster again in his prime for one hour. This agreement cost the life of one of the Fluorescent Five. After the hour, Jim's soul would be frozen in ice for eternity.
Jim Stearn arrived just in time to save his son from his mother and her three vampire brothers (two of which Strongfort managed to kill himself). After Jim killed the third brother, Lillith shot Jim with a crossbow, killing him. Strongfort then took the arrow out of his father and killed his mother with it. Afterwards, the Fluorescent Five wiped Strongfort's young mind clean.
Eventually, the Fluorescent Four began regretting putting Jim's soul in a block of ice. The knowledge of the Mr. Monsters was also trapped inside and couldn't be given to Strongfort. They asked Strongfort to free his father's soul from the block of ice by shattering the ice, but Strongfort resented his father for the fact that his father had quit being Mr. Monster early in his career.
Confronted by his girlfriend Kelly Friday (daughter of Joe Kelly and Gloria Greene) about his childhood, Strongfort's memories returned and he finally forgave his father for quitting being Mr. Monster, thus freeing Jim's soul from the iceblock. Jim's soul said his goodbyes to his former lover Gloria, her husband Joe Friday, their daughter Kelly and especially his son Strongfort, telling them he loved them.