Starbright

If they fail, their world will end…
Banished from her kingdom by the evil Queen Morag, Princess Gwyneth, a young sorceress, is forced to undertake an urgent and perilous quest to recover a powerful ring from the bottomless Well of Souls, deep inside the dreaded Spider Forest.
But first Gwyneth must rescue Starbright, a unicorn, imprisoned inside The Crystal Mountain. Because only Starbright's horn can neutralize the poisoned water in the Well of Souls.
On a journey fraught with danger, Gwyneth is confronted by every nightmare she's ever had, plus some she never could have imagined. Along the way, she rescues a fish from a dying lake, a hive of bees from a fire, and a falcon from a deadly eagle attach. Unable to leave them behind to face certain death, she takes them with her.
In the final, cataclysmic showdown at the Well of Souls, as Gwyneth and Morag are locked in a battle to the death, the Princess discovers that even the smallest creatures can be powerful allies. And that not everything is as it seems.