The Magnetic Field Disruptor or MFD is a Reach weapon. Once they reach "chrysalis" mode, they cause a deterioration of the planet's magnetic field that will destroy the world. The disruptors are capable of operating in hostile environments such as sub-zero temperatures and deep underwater.
Black Beetle and the Reach activated magnetic field disruptors in twenty-one locations around the Earth. Each disruptor was guarded by a number of Beetle-tech Drones, each drone the equivalent of a Beetle warrior, which would remain active until the disruptor builds enough energy in order to "go chrysalis". Once this happened, the resulting magnetic instability would cause the planet to destroy itself, thus hiding all evidence of Reach tampering on Earth from the Green Lantern Corps, which was otherwise a violation of the treaty signed by both parties.
Blue Beetle collaborated with Lex Luthor to counteract the disruptors. He provided Reach-tech Eggs, which Luthor laced with an anti-Reach virus software created by LexCorp; a mere touch would render the disruptors inert. Forty of Earth's heroes, working in pairs, succeeded in defusing twenty of the disruptors, and destroyed the drones guarding them.