Potenta Crystal

The Crystal of Magic can be used to amplify or dampen spells. In the Great Apocalypse, the Dark Elves used it to power their stasis that kept a protective bubble around the dormant city until they were awoken when Gaerel stole it to use at the battle of Castle Yag Zhu Ruins. The crystal passed to the Academy, then to the vault under King Gratum's castle in Capital City, before being returned to the Dark Elves.
More recently Gaerel stole the crystal again and made his way to Kithaern, where he was again aprehended.
One of the 7 Crystals of Power