Lily Quench and the Magician's Pyramid — Natalie Jane Prior

In a dense wilderness far to the north is a gigantic pyramid filled with secrets. It is home to three evil magicians who built the Eye Stones: sinister doorways in time that Lily Quench and Queen Dragon are determined to close off forever.
 
When Queen Dragon vanishes, Lily fights alone to uncover the pyramid's mysteries. What is the dreadful truth behind the magicians' unnaturally long lives? Who -- or what -- is being hidden inside the pyramid? And what has happened to Queen Dragon? Lily faces her most dangerous adventure yet.