Dread mountain. Emily Rodda. 2000.

Lief, Barca and Jasmine are on a perilous quest to find the seven lost gems of the magic Belt of Deltora. Only when all the gems have been restored to the Belt can Deltora be freed from the tyranny of the evil Shadow Lord.

Four gems have been found. Now, though grave news reaches Lief from home, and he longs to return, the quest must continue. To find the fifth stone  the heroes must venture almost to the border of the Shadowlands, and plunge into the darkness and terror of the realm of the monstrous toad Gellik - Dread Mountain.