Rhianna and the Castle of Avalon

Third book in the children's medieval fantasy-mystery series, Rhianna. At the Queen's command, Rhianna must travel to the Castle of Avalon to seek her magic powers from the evil Wild Magic, who lurks in the castle's secret tunnels and passages. The previous volumes are 'Rhianna and the Wild Magic' and 'Rhianna and the Dogs of Iron'.