Under the Stone of Destiny (Celtic Otherworld, #1)

Four teenagers are trying to end the ruinous war. They are a human, a runaway Elf Princess, a Dryad Mage and a Dwarf Wizard. Or at least that's what Caoimhghín (Kevin), the student Magus thinks they are.
Most of the action is on a legendary Celtic Otherworld, in Magh Meall where all the Tuath Dé live. Out of food and close to despair in the mountains they are told to wait for another companion by Corbie, the rook Familiar of Dean David, from the Magi College.
The cover is edited from a detail...