"You cannot harm one who has dreamed a dream like I have."
- – Jason Ironheart
Jason Ironheart was a telepath, member of the Psi Corps and a former lover of Talia Winters. After an experiment in which his telepathic abilities were greatly enhanced, he became a new being and left humanity.
In the mid-23rd century, Ironheart was an instructor at the Psi Corps Academy, specializing in, among other things, fringe skills. While working as an instructor, he helped to teach and train Talia Winters and the two had, by Winters' account, a brief but passionate affair. The two would remain in touch over the succeeding years, albeit sporadically, until 2257.
In that year, Ironheart volunteered for a secret project and underwent a variety of treatments with the goal of creating more stable and powerful telepaths. Thinking this would be for defense of stations and important officials, Ironheart was eager to be successful. Over the next several months, the project involved genetic manipulation and injections of acetylcholine and mutated serotonin by the Corps to enhance his telepathic ability and to attempt to create a stable telekinetic. The schedule was grueling, involving multiple shots a day at some points, however, the experiment was successful. His powers grew to an unmanageable level. He was able to pierce any telepathic block, however, this allowed him to learn the truth about the Psi Corps: that they were expanding their powers and influence in Earthgov rather than under their authority as the public believed. He also realized they wanted assassins who could kill without leaving a trace. He couldn't allow them to have that power, so he killed the head researcher, the only one who could replicate the experiments, and fled.
He and another telepath escaped on a stolen transport and decided to head to babylon 5 where Winters was stationed, hoping she could help him stay calm and control what was happening to him. On the way, he was approached by Black Omega fighters, but he easily destroyed them. He made it to B5 but so did Psi Cops Alfred Bester and Kelsey. Ironheart knew the Psi Cops would approach Jeffrey Sinclair to help them apprehend Ironheart and to question Winters on her contact with him. Ironheart waited until Winters was subjected to a painful joint deep scan by the Psi Cops before approaching her. She initially refused to be involved, but Ironheart insisted to talk in private, so they retired to Winters' quarters. Once he told her what he had found out or otherwise surmised about the Psi Corps' goals, she was visibly shaken. Both persuaded Sinclair that Ironheart's powers were too dangerous to be claimed by the Psi Corps, who wished to create telekinetic assassins. Sinclair agreed to help him escape ordering a fake safety drill to evacuate the route to Ironheart's escape.
Escorted by Winters and Sinclair, Ironheart hurried to his ship but was interrupted by Bester and Kelsey. Sinclair subdued Bester, but Kelsey was determined to stop Ironheart, drawing her PPG. He pleaded with her to stop, but had to vaporize her. In the turmoil and mindquake he managed to exit the station onboard his ship.
As his ship hovered nearby, suddenly an energy field enveloped it. His powers grew to such a level that he ascended into a being of pure energy. Before departing, he thanked Sinclair, telling him that he would see him in a million years. Unbeknownst to Sinclair, he was referring to when humanity will have evolved into Vorlon-like energy beings. 
As a final gift to his former lover, Ironheart gave Winters rudimentary telekinetic powers.