Holder of Lightning — S.L. Farrell

It had been so many generations since the mage-lights were last seen that they'd become the stuff of legend. But for seventeen-year-old Jenna Aoire legend became reality one night on Knobtop Hill when she found the stone--not much more than a large pebble yet there was something about it that drew her. And then the mage-lights filled the sky.
When the lights came, trouble and magic followed, and Jenna's life and future were irrevocably altered. For the stone which had called to her was a cloch no thintri, the spell-stone of a cloudmage. In fact, what she held was the Lamb ShAllah, the master stone that was the only means to reawaken the power of all the other clochs.

But those who would seize control of magic could not do so unscathed, and she who was the First Holder of Lamh Shabhala must bear a greater burden than any other cloudmage.

For Jenna'becoming First Holder meant putting much that she held dear behind her as she and her mother Maeve were forced to accept the aid of one lord while fleeing the greed of many others. Yet even in the sanctuary that Tiarna Mac Ard offered Jenna and Maeve, treachery and betrayal would shadow Jenna's every step. Soon she would find herself at the heart of a deadly maelstrom of elemental forces, torn between the demands of rival factions and of Lamb Shdbhdla itself. Only time would tell whether she was truly destined to be First Holder or whether she must give up both the cloch and her life to those who were older and more cunning, nobles who had spent their entire lives preparing to snatch for themselves the power which had marked Jenna as its own....