Many centuries ago, the man now known as General Immortus gained a supply of a certain chemical that allowed him to survive down the ages. As the years passed, Immortus paid the greatest chemists in history to duplicate the chemical, but none could do so. At last, in the 20th century, with only enough chemical left for two more centuries, Immortus became desperate. Since one more attempt to duplicate his chemical would exhaust his remaining supply, Immortus became the secret benefactor of Niles Caulder, a brilliant young scientist who was pursuing his own research into the secret of immortality.
When Caulder learned that Immortus was his benefactor, he refused to continue his research, but Immortus forced him to do so by implanting a miniature bomb in the young man's chest. Ultimately, Caulder tricked Immortus into shooting him as part of a plan to free himself from Immortus' domination. Though Caulder was able to have the bomb deactivated, the effort left him a paraplegic, his legs totally useless.
To combat Immortus, Caulder gathered a group of super-powered misfits he called the Doom Patrol. For years the Doom Patrol battled Immortus and his ilk, until Caulder and his team were seemingly slain by two of their foes. Fearing the secret of immortality was lost to him forever, Immortus was relieved to find that Caulder had passed the secret to his wife Arani who had organised a reformed Doom Patrol.
Immortus kidnapped Arani and used his super-science to probe her mind and discover at last the secret he had sought for centuries.
After drinking the immortality serum, Immortus grew stronger, more virile, and became a young man again for the first time in centuries. But the effects of the serum, which had been specially formulated for Arani's unique body chemistry, were short lived and Immortus became an old man again, apparently perishing in the destruction of his mountain headquarters.
However, he later appeared as one of the villains stranded on planet Salvation. He was apparently killed in the Parademon attack. However he has recently appeared on Earth alive, as the leader of a group of low list supervillains called the Army of the Endangered. During this time, he had a moll called the Seductress, whom he promised his fortunes to when he died, as she did not know the meaning of the term immortal. Immortus had also enlisted the aid of Professor Milo to perform super surgery on people to give them super powers. One such person, the criminal called the Human Flame, ultimately betrayed the team.
Some time later, the Doom Patrol meet Immortus at a ball held by the Aristocrats. He warns them that though he will not harm them because of etiquette, but their leader, Veronica Cale, will not live to see the morning.
Immortus is a master strategist having lived for centuries.
In other media
General Immortus appears in the 5th season of Teen Titans as a member of the Brotherhood of Evil. He doesn't have many appearances.