Into the Narrowdark — Tad Williams

The New York Times bestselling world of Osten Ard returns in the third Last King of Osten Ard novel, as threats to the kingdom loom...

The High Throne of Erkynland is tottering, its royal family divided and diminished. Queen Miriamele has been caught up in a brutal rebellion in the south and thought to have died in a fiery attack. Her grandson Morgan, heir to the throne, has been captured by one of Utuk'ku's soldiers in the ruins of an abandoned city. Miriamele's husband, King Simon, is overwhelmed by grief and hopelessness, unaware that many of these terrible things have been caused by Pasevalles, a murderous traitor inside Simon's own court at the Hayholt.
 
Meanwhile, a deadly army of Norns led by the ageless, vengeful Queen Utuk'ku, has swept into Erkynland and thrown down the fortress of Naglimund, slaughtering the inhabitants and digging up the ancient grave of Ruyan the Navigator. Utuk'ku plans to use the Navigator's fabled armor to call up the spirit of Hakatri, the evil Storm King's brother.
 
Even the Sithi, fairy-kin to the Norns, are helpless to stop Utuk'ku's triumph as her armies simultaneously march on the Hayholt and force their way into the forbidden, ogre-guarded valley of Tanakirú -- the Narrowdark -- where a secret waits that might bring Simon's people and their Sithi allies salvation -- or doom.