Riven

⭐⭐⭐⭐⭐ "Couldn't put it down . . . sat up reading all night . . . an epic." -Amazon reviewers

Augum, Bridget and Leera want only to study new spells and make their legendary mentor proud. But when she unexpectedly departs on a crucial quest, they run afoul of a devious old witch and are forced to make a hasty getaway-straight into the hands of a notorious maniac known as the Blade of Sorrows.

Prisoners of the Blade and his sadistic apprentice, the trio must face their greatest challenge yet: escape using nothing but an ancient spell with some nasty side effects. But more than their lives are at stake, for an entire kingdom's hopes rest with their mentor-and she's heading for a deadly trap.

The complete Arinthian Line series:

ARCANE (The Arinthian Line, Book 1)
RIVEN (The Arinthian Line, Book 2)
VALOR (The Arinthian Line, Book 3)
CLASH (The Arinthian Line, Book 4)
LEGEND (The Arinthian Line, Book 5)