The Girl Who Braved the Underground. Fairendale, #16

Only the bravest will survive what lies underneath. Thumbelina, one of the lost children of Fairendale, finds herself all alone beneath the ground of Ashvale, thanks to a Vanishing spell that transported her to the abandoned land. She carves out a home for herself, fashioning furniture from scraps of tree limbs, persisting on a paltry diet of leaves, and staying clear of the Fire Mountains that destroyed the land and its people eight years ago.
All she really wants to do is return to her homeland of Fairendale, but she is too small to do anything that great-or so she believes. When an unexpected visitor invades her underground cave, requesting her help rescuing a trapped toad king, Thumbelina wonders: Can she do something great? Save the toad king from his captivity? Prove that she is small but mighty? Spurred by a victorious attempt, Thumbelina bravely faces a stag beetle, a frozen bird, and a mole.
But when a wicked sorceress traps her in a shrinking cage, Thumbelina's newfound confidence diminishes, and she faces her most harrowing decision yet: Stay in the cage or defy one who is much larger and more powerful than she is and so save all who need saving. The Girl Who Braved the Underground is the sixteenth book in the Fairendale series, an epic fantasy middle grade series that explores both familiar and unfamiliar fairy tales, legends, myths, and folk tales.
The world of Fairendale revolves around villains and heroes-all on a quest for what they believe is right. Throughout the series, the story of King Willis and his determination to keep the throne of Fairendale (at all costs? Perhaps. Or perhaps not.)  is woven into the story of his son, Prince Virgil, heir to the throne and friend to the village children, and the story of fairy tale children fleeing for their lives-children who become what we know as fairy tale villains, for one good reason or another. But, remember, one cannot always know, at first glance, who is the villain and who is the hero.