A Locus Magicalicus is a center of power for wizards in the city of Wellmet, and the cities beyond. The appearance and power of these stones vary with the person that the stone has claimed. These stones allow the wizard to communicate with the magic around, and will not work if there is no magic nearby. The dragons notice specific stones because these stones were part of its hoard from before it turned into magic.
When the wizard dies, his or her soul or essence goes into the locus magicalicus. If a wizard attempts a spell more powerful than their locus magicalicus can handle, they will die and the stone will shatter, never to be used again.