Energy magnet

An energy magnet is a device which can wirelessly drain energy from miles around. So large that it has to be built into the top of a tower, it can pull energy from whole cities.

The Transformers cartoon
While creating electrodes for the Decepticons' new energy magnet, Megatron inadvertently created a small energy-based life form which he named Kremzeek. Though the creature was an unintended byproduct, it kept the Autobots busy long enough for the Decepticons to complete the energy magnet at the top of a tower at about 200 miles offshore from Tokyo.

The first test was successful and a number of nearby ships were suddenly without power. Megatron prepared for a longer-range test, but Starscream was impatient and fired the energy magnet up to full power. The magnet began draining power from far off cities, including Tokyo, where the Autobots had pursued Kremzeek. The Autobots lured Kremzeek to Tokyo Tower, beaming the creature to the energy magnet and destroying it as the Decepticons fled.