Decepticon War Machines are very large weapons that the Decepticons used to resist the Autobots during the Great War. Their primary use is to spread Dark Energon crystals, though they are also armed with an impressive array of weapons, including homing missiles and beam weapons. They are also known as Dark Energon corruptors.
Optimus Prime, Ratchet, and Bumblebee had to fight their way through several Decepticon War Machines on their way to the Decagon to reestablish Iacon's communications and coordinate its defense. Optimus recognized the weapons from information stored in the Archives.
After gaining control of Trypticon station, the Decepticons used Dark Energon corruptors to spread the substance across Cybertron's major cities, including Iacon. They were also used to spread the infection to the planet's core.