The Dark-Heart NanoTech (DC Animated Universe)

The Dark Heart was a highly advanced alien construct capable of endlessly recreating itself via the use of nanotechnology.
Powers: Cloning and Material Conversion
50,000 years ago, two worlds were at war. One created a war machine composed of nanotechnology. When sent to another planet, it begins to duplicate itself and overrun everything. In the process, the machine uses any material it can to duplicate, animate and inanimate. The machine accomplished its task but kept on duplicating. Across time, the Dark Heart spread. The Dark Heart has demonstrated the ability to create three types of drones; a small insect that mainly seeks out materials, a tiger-like drone that is more offensive and a larger scale insect. The materials collected are sent back to the central dark heart in liquid form through artery like constructs. The Atom was able to expose its only weakness, to 'clog' an artery and cause an overload. The U.S. military took the alien remains away to be disposed of but most of the Justice League Unlimited remained skeptical of its future.
The remains of the Dark Heart were confiscated by Cadmus. However, the technicians under the employ of Cadmus could never re-activate them. They were stored away in the main Cadmus facility in Washington DC. Being the most sophisticated nano-technology on Earth, the Dark Heart became the target of Lex Luthor and Brainiac in their bid to become gods and remake the universe. After assimilating a drone's nano-assemblers, Brainiac gained the ability to create anything from raw material and the duo moved forward with their plans.