Three years after finishing The Elfstones of Shannara, Terry Brooks wrote the final book in what would eventually be known as The Sword of Shannara Trilogy. This book was The Wishsong of Shannara.
The book takes place a little over twenty years after the events in Elfstones. Wil Ohmsford is now married and has two children. He has a daughter named Brin and a son named Jair who both have innate magic due to Wil's actions in Elfstones. The plot revolves around the origins of the Warlock Lord and the source of his power. It is revealed to have been an ancient book, known as the Ildatch and in order to destroy this book and its evil once an for all, the druid Allanon recruits Brin to help him penetrate a great swamp that holds the book. Standing against them is an army of gnomes and servants to the power of the Ildatch, known as Mord Wraiths who will do all in their power to stop them.
Parallel to Brin's journey is Jair's. He is recruited by a benevolent creature, known as the King of the Silver River, to purify the corruption the Mord Wraiths have caused, and to aid Brin when her quest comes to its end.
While not quite as good as Elfstones, this book is a great edition to the series. Brin and Jair were forgettable protagonist, but this book introduced some of the greatest supporting characters of the series. These characters include Slanter, an abrasive gnome tracker. Initially hired by the Mord Wraiths to track down Allanon, he becomes a reluctant companion in Jair’s quest and one of his best friends.
The book also introduces the character of Cogline, a half-mad man, with a knack for explosive powders and would be a major character in future books. This was also the first book to introduce the creatures called Moor Cats and the reptilian creatures known as Mwellrets, who would have roles in many more of the Shannara books.
In this book Allanon’s character has changed once again. In Sword he was a leader, not unlike to Gandalf in The Fellowship of the Ring. In Elfstones he was a warrior druid who did a lot of the fighting himself. In this book, he came off as a world weary old man, who seemed like he was trying to finish his work before he dies.
The most noteworthy of these characters,however, is Garet Jax, the Weapons Master. He's the ultimate fighter of the series, able to kill anything in his path with any weapon and searches the world for an ultimate challenge that will truly test his skills. While a little cliched by today’s standards, he's a great and mysterious character who was undoubtedly one of the best in the Shannara series and it's a bit of a shame that this is the only book he appears in. He joins Jair on his quest only because The King of the Silver River promises him that he will have the fight of his life when the journey comes to its end.
Another noteworthy creature is the Jachyra. It's a demon that the Mord Wraiths summoned to guard certain areas, who's claws and teeth poison not only the body but the sole as well and make for great creatures for the protagonist's to fight.
This book also probably has one of the highest death rates in the Shannara books, as many major characters die, giving a darker feel to it. It was also the first book to bring forth the idea in the series that magic is addicting and is as deadly to the wielder as the wielder's enemy. The groundwork for this had already been in place in earlier books but this was the first to really bring the concept out and would be repeated many times throughout the series.
The ending was a bit campy but conclusive and Terry Brooks could have easily ended the series here. Oddly, the book spawned a short epilogue story called Indomitable and a comic book entitled The Dark Wraith of Shannara that continued the journeys of Jair after Wishsong had ended, but neither are required reading to understand the series. While this book wasn't quite as good as Elfstones, it was close and I would recommend reading it if you like the previous two books.