The Druid Of Shannara: The Heritage of Shannara, book 2

To the scions of Shannara have fallen three tasks: Par Ohmsford has recovered the fabled Sword of Shannara. This he has accomplished, but the Federation's Chief Seeker has planted an awful thought in Par's mind - that he himself is Shadowen, the very evil he seeks to destroy. Wren is in the Westland, seeking out the elves. And in the Northland. . .
Walker Boh has been commanded by the shade of Allanon to find the lost city of Paranor and recreate the Order of Druids, disbanded for three hundred years. To achieve this he must find the Black Elfstone, but the gem is in the hands of an ancient being of timeless evil - the Stone King. Beset on all sides by enemies, and from within by his own self-doubt, Walker Boh sets out on his part of the perilous quest. A quest that will end in success - or the complete destruction of all he holds dear.