The secret of the sword - Terry Brooks

Cut off from his friends and the Druid Allanon, Shea remains determined to continue his pursuit of Orl Fane, the crazed gnome who has stolen the fabled Sword of Shannara.
Fane's tracks suggest he is headed north to Skull Mountain, lair of the master of all that is evil. If the gnome is not stopped, and the Sword delivered into the Dark Lord's hands, all hope for the races of the Four Lands will be lost forever.
And time is already running out, for even as Fane flees with Shea in pursuit, the Warlock Lord summons a vast army of gnomes, trolls and northmen. Under the command of his dreaded Skull Bearers they begin the march south - with plans to annihilate all in their path.
And so the classic tale of magic, adventure and epic conflict that is the legend of The Sword of Shannara draws to its unforgettable conclusion.