The Original Shannara Trilogy Series by Terry Brooks (4 Book Set)
The 4-book set of mass market paperback novels includes the below titles:
First King of Shannara (ISBN 9780345396532): Horrified by the misuse of magic they had witnessed during the First War of the Races, the Druids at Paranor devoted themselves to the study of the old sciences, from the period before the collapse of civilization a thousand years before. Only the Bremen and a few trusted associates still studied the arcane arts. And for his persistence, Bremen found himself outcast, avoided by all but the few free-thinkers among the Druids.
But his removal from Paranor was not altogether a terrible thing, for Bremen learned that dark forces were on the move from the Northlands. That seemingly invincible armies of trolls were fast conquering all that lay to their south. That the scouts for the army–and its principal assassins–were Skull Bearers, disfigured and transformed Druids who had fallen prey to the seductions of the magic arts. And that at the heart of the evil tide was an archmage and former Druid named Brona!
Using the special skills he had acquired through his own study of Magic, Bremen was able to penetrate the huge camp of the Troll army and learn many of its secrets. And he immediately understood that if the peoples of the Four Lands were to escape eternal subjugation they would need to unite. But, even united, they would need a weapon, something so powerful that the evil magic of Brona, the Warlock Lord, would fail before its might…
The Sword of Shannara (ISBN 9780345314253): Living in peaceful Shady Vale, Shea Ohmsford knew little of the troubles that plagued the rest of the world. Then the giant, forbidding Allanon revaled that the supposedly dead Warlock Lord was plotting to destory the world. The sole weapon against this Power of Darkness was the Sword of Shannara, which could only be used by a true heir of Shannara–Shea being the last of the bloodline, upon whom all hope rested. Soon a Skull Bearer, dread minion of Evil, flew into the Vale, seeking to destroy Shea. To save the Vale, Shea fled, drawing the Skull Bearer after him….
The Elfstones of Shannara (ISBN 9780345285546): Thousands of years after the destruction of the age of man an d science, new races and magic now rule the world, but an imminent danger threatens. A horde of evil Demons is beginning to escape and bring death upon the land. Only Wil Ohmsford, the last of the Shannara bloodline, has the power to guard the Elven Princess Amberle on a perilous quest to the save the world, while the leader of the Demon force aims to stop their mission at any cost.
The Wishsong of Shannara (ISBN 9780345356369): An ancient evil is stirring, intent on the complete destruction of all life. The Druid Allanon sets out on a dangerous journey to save the world, reluctantly aided by Brin Ohmsford, daughter of Wil Ohmsford—for she alone holds the magic power of the wishsong. But a prophecy foretells doom, as evil nurses its plan to trap the unsuspecting Brin into a fate far more horrible than death.