Earth-Scar by Laurie Mahon

Princess Selina is more than just a royal - she's a warrior. When a bloodied scout staggers into her father's court with an ancient Dwarven recording stone, the kingdom learns of a forgotten secret: five legendary Orbs, which, when united, can destroy the undead. But one is already in enemy hands. With her mentor, Elven Marshal Ryfon, and quick-witted wizard friend, Felix, Selina sets out to recover the Orb. The chase leads them into Earth-scar, a dangerous canyon on the verge of collapse. Brute strength won't be enough. Selina will need cunning, courage, and a little bit of luck to succeed. The battle to save the Openlands is only just beginning.
Binding: Paperback / softback