Mai-Otome Zwei/WMG

The Surrogate System is powered by discardable clones of Fumi Himeno.
How else would Garderobe, with its limited understanding of Otome technology, convince the system that the contract was genuine, if not by using a system of People Jars reminiscent of the one used to produce Dummy Plugs in Neon Genesis Evangelion? This also explains why each "core" can only operate for limited time: due to accelerated growth, each clone deteriorates rapidly under physical stress that comes from being contracted to an Otome.
 * Possibly, this is the Dummy Plug system. This dovetails nicely with the Evangelion theory on the Mai-Otome page.