Per Degaton has a complex backstory. Yes, I know that it's shocking to hear that a time traveler has a confusing origin so I'm going to attempt to make this as basic as I can. Degaton was an assistant in a group of scientists called the Time Trust during World War 2 that were attempting to find a means for bomb defenses in the future to help the war effort in their time. The Justice Society of America went 500 years into the future and returned with the formula to produce such defenses. Enraged and jealous of the JSA Degaton sabotaged the formula before abandoning the Time Trust.
Obsessed with time travel Degaton had many run ins with heroes before coming in contact with a robot from the future named Mekanique. She helped him learn more of his passion. During their first five years together her body was crushed leaving only her head. Spending time together the two fell in love. (Don't you love comics?) Professor Malachi Zee, like Degaton a former member of the Time Trust, worked with the two to create a time machine. In one of the many ironic twists in his life Degaton aims to kill Zee unintentionally sending him 40 years into the future in a time machine he intended to use for his own purposes. Mekanique suggested they wait for it to reappear which drove Degaton over the edge to the point where he buried her head.
The moment that's retconned: Originally Degaton carries on with his dastardly plans living out most of the next 40 years behind bars. Once he's out he reconstructs Mekanique and he battles the Infinity Inc. in the same spot that the Zee time machine disappeared where it soon reappears. A dying Zee comes out along with a Chronal Duplicate of Degaton made when he attempted to stop the time machine from leaving. The old Degaton commits suicide rather than return to jail and Mekanique gets her revenge by killing the double. In the retconned version the duplicate tries to change his fate prior to these events only to return to relive the same moment in a time loop when he is defeated. He recalls all these failures each time he returns to the same moment.
Accepting that on some level that he will never win against the JSA Degaton existed as a non-linear ghost like being that repeatedly watched his enemies dying taking pleasure in witnessing their pain. He lives "between the seconds" as an ageless eternal being thanks to his Time Disk which he sometimes uses to travel. Tachyons like the ones found in Hourmans' hourglass are able to get him out of his intangible state. Degaton has been able to break the pattern of the time loop since aquiring the time disk to watch more of his foes suffering.
Team Ups: The original worked with the Time Trust, and Mekanique. The duplicate has genetically advanced soldiers from the year 2666 called the Red Morgue that he uses as his own personal assassins. He has also teamed up with other time displaced villains to form the Time Stealers.
Enemies: He has an intense hatred for the JSA and his biggest rival in time travel appears to be Rip Hunter who Mr. Mind promised he could personally kill.
A/N: Because of the long history involved I have decided to only write about the Time Stealers that have previous history in time travel, i.e. Mr. Mind and Black Beetle.