  Magnetic energy is one the main agents powering our society: generating
energy in power plants, keeping information in magnetic memories, moving our
devices with motors. All of these applications require a certain spatial
distribution of magnetic energy, for example concentrating it in a transformer
core or in a magnetic sensor. We introduce in this work a way to collect
magnetic energy and distribute it in space with unprecedented efficiency and
flexibility, allowing very large concentration of magnetic energy in a free
space region, an enhanced magnetic coupling between two magnetic sources, and
the transfer of magnetic energy from a source to a given distant point
separated by empty space. All these features are achieved with a single device,
a magnetic shell designed by transformation optics.
