It's a powerful form of anti-matter that was created by Praxis.
Adam Worth believed it had infinite possibilities and uses, but the praxian government believed it was too unstable for its' energy to be harnessed.
Despite their warning, Adom experimented with the device while in Praxis. His experiments destoyed an entire section of the city and killed 200 citizens. It's for this reason the Praxians executed him. However, Fallon resurrected Adom and helped him escap to the surface. Adom promised Fallon that if she helped him he'd help her by giving her control over Praxis' defense systems so she could lead a revolution against the city. Adam then infected himself and Helen Magnus with radiation poisoning knowing she'd go to Praxis to get the cure. Adam followed Magnus to Praxis where he stole the device and tried to take it out of the city only to be stopped by John Druitt. The device was then returned to Praxis. It was thought John had killed Adam, but it was later revealed that John and Adam had made a deal. Adam told John that he planned to use the device to create a time machine that'd allow him to go back to the past and save his daughters life. Adam promised John if he'd let him live then
The device along with a message left by John.
he'd allow John to use the time machine to prevent the five from ever using the Source Blood so no one would think he was Jack the Ripper and Helen and him could be together. Adam made a copy of the devices specifications before sending it back to Praxis in order to create his own device later. Adam eventually did create his time machine and it was powered by his copy of the device. He used it to go back in time to 19th century London, but also destroyed Praxis in his experimenting.