Powerstone

Powerstones are the enigmatic gems once utilized by the Thran to power countless devices of theirs. Urza and Mishra also coveted them to a great deal, and used many powerstone-fueled devices in the Brothers' War. The legendary Mightstone and Weakstone were each half of an extremely powerful powerstone. Nobody is completely sure where these rocks come from. But the Thran artificer Glacian did learn something interesting about them: the non-magical energy inside a stone can actually be restored or enhanced by absorbing space itself from a surrounding plane. Techniques to do so were used to devastating effect during the Thran-Phyrexian War. Given that powerstones have the energies they do, it could be that they all contain a great deal of space locked within, possibly even an entire collapsed plane. Powerstones are not without risk however. When his exile to Thran was revoked so as to garner help in dealing with a plague known as phthisis, Yawgmoth revealed that prolonged exposure to the stones can result in a sort of radiation poisoning, the effects being greatly similar to tuberculosis in the real world.