Sylbert Rundine was a student and serial killer who stalked the dormitories of Ivy University. He acquired a Bio-Belt similar to the one worn by college professor Ryan Choi and became the psychotic super-villain Dwarfstar.
By the time of his last appearance, he was revealed to be the "first son" of Jia, a.k.a. Lady Chronos. Having been aged due to a forced stay in a time-accelerated micro-universe, he was left even more mentally unhinged than before. He vanished along with Chronos and Lady Chronos.
In the "Titans: Villains for Hire" one-shot, Dwarfstar had paid Deathstroke to assassinate The Atom IV (Ryan Choi). He is last seen holding a small matchbook containing the body of his long time nemesis after assuring Deathstroke that the "transfer's done". After this, he signs up with Bane as one of the new members of the Secret Six.
Unfortunately for Dwarfstar, Giganta was also on the new Secret Six team. He was unaware of Giganta's personal relationship with Ryan Choi. After their mission was complete, Amanda Waller decided Dwarfstar was too much of a loose cannon. Needing him out of the way, she informed Giganta that Sylbert had had Ryan killed. Giganta invited him back to her hotel room for what he thought was to be a late night hook-up. It was heavily implied that, at the least, she hurt him very badly.
Dwarfstar makes a cameo appearance in the Batman: The Brave and the Bold episode "Sword of the Atom" as part of a montage to the original Atom Ray Palmer.