Keeper of Light[s] - Hodder Silver Series

In disgrace after her last dangerous display of her power, Shar is forbidden from dabbling in any magic without the explicit permission of the High Initiate. But then Shar hears of an unprecedented experiment the High Initiate is conducting with the other Circle Adepts. The Circle's plan is to unlock the secret of the Maze - a magical gateway through time - and freely explore other worlds, times and universes. But their plan doesn't work and Shar cannot resist attempting the experiment herself. Using every ounce of her unique power Shar is determined to succeed where the Circle has failed. At first she simply enjoys whizzing through time, visiting her ancestors, but when she discovers she can change the course of history, she has a shocking realisation: she can prevent the death of her parents and avenge their killer! But with this chance comes chaos and destruction and quite possibly Shar's own death. Can she take such a risk this time?