Maxwell's Demon Stone
From OMGWiki
A Maxwell's Demon Stone is a powerful spirit stone. It sort of acts like a steam generator. Maxwell allows fast moving molecules into his room, while keeping out slower ones. This creates heat buildup. After reaching a critical mass, the demon pushes out the heat and he repeats the cycle. This stone appears in Chapter 21, The Secret's Out, when Belldandy puts it into a regular broom to make it fly. It should be noted that this stone shares its name with a real life thought experiment, Maxwell's Demon, which proposed a small "demon" to regulate temperature flow.
