The Wishsong of Shannara (The Original Shannara Trilogy #3)

Horror stalks the Four Lands. The Ildatch, immemorial book of evil spells, has stirred to eldritch life, sending its foul Mord Wraiths to accomplish at last Mankind's destruction. Once again Allanon, ancient Druid Protector of the Races, must seek the help of a descendant of Jerle Shannara. Brin, daughter of Wil Ohmsford, born with the magic of the Wishsong which alone can open a way to the Ildatch, reluctantly joins him on his perilous journey east; meanwhile her younger brother Jair learns that Brin will fail and die, unless he can reach her in time. And as Brin walks into the trap the Ildatch has set, Jair must travel through the very heart of evil to reach her...