Straken

Young Penderrin Ohmsford is charged with the daunting task of rescuing his aunt Grianne, Ard Rhys of the Druid order, from her forced exile in the terrifying dimension of the Forbidding. Though Pen enlists the support of the noble dwarf Tagwen and the elven princess Khyber Elessedil, the mission will not be without risk ... or sacrifice. For the ruthless Druid Shadea a'Ru has sent her agents and assassins in relentless pursuit of Pen and his comrades. If Pen fails, Shadea's domination of the Four Lands will be assured. The task grows even more dire when Pen's parents fall into Shadea's hands. Yet all challenges pale in comparison to the horrors that wait inside the Forbidding -- horrors poised to break free upon the Four Lands.

This is #3 in High Druid Of Shannara Series.