The Third Door by Emily Rodda - USED

Rye and Sonia have faced the heart-stopping perils of the land behind the golden Door, and the cold terrors that lurk behind the silver Door as well. By a miracle, they have survived them both. But Weld is still under threat, and many questions remain to be answered. Rye knows what he has to do. One Door remains a mystery-the ancient wooden Door that he has been drawn to from the beginning. All he has to do is dare to go through it.