Shadow chaser book two of the chronicles of siala

"Facing formidable magical monsters who have defeated countless armies and wizards, a grief-stricken Harold and his surviving companions endeavor to gain a magic horn to save their land from The Nameless One."
"Shadow Harold, master thief, is in over his head. When he accepted the King's commission (not that he had any choice in the matter) he did not think that it would be to retrieve a legendary artefact from Hrad Spein, the many-layered resting place of ogres, elves and wizards; a place of dread, awe and immeasurable power, sealed up for centuries."
"Saddened because they have left one of their number in a grave in the wilderness, Harold and his companions continue their journey to the dreaded underground palace of Hrad Spein. There, knowing that armies of warriors and wizards before them have failed, they must fight legions of untold, mysterious powers before they can complete their quest for the magic horn that will save their beloved land from the Nameless One."@en
"Een dief vertelt hoe een groep mensen een queeste onderneemt om een magische hoorn te vinden."