The Prometheus Weapon was a theoretical weapon, credited by Dr. Julia Cathcart, that was stated to be powerful enough to wipe out all but the most primitive life on Earth. The weapon was believed to have ended the war between the Chimera and the creators of the Gray Tech components, and speculated it is what buried the Chimeran tower network - presumably it was also the cause of the Chicxulub asteroid impact - and forced the Chimera to completely evacuate from Earth. After the weapon was used, for reasons unknown (probably due to the weapon's destructive potential), it was disassembled and its pieces scattered across Earth.
The weapon's very existence was deduced by SRPA scientists to be the result of combining Gray Tech components that the Chimera were deeply searching for, but it was never completed. Daedalus was believed to have been attempting to recreate the weapon at the Holar Tower, but was stopped by SRPA forces.