Phillip and Whizzy (Book 3): Last Emerald

Phillip Harper and Michael "Whizzy, Whizzenmog need to return to Mistasia in order to save Grace Tallon and stop King Cragon Cadieux who once again rules Mistasia. In order to return, they must convince, Rachel and Whizzy's grandfather, Rainer Whizzenmog to help them with the use of a mystical green emerald.
Their travels through Mistasia will be more dangerous than ever before, as King Cragon and his heinous sorcerer, Pierre LaCroiux will stop at nothing to keep them from reaching the castle.
Unexpected, new friends and foes will force Phillip, Whizzy and Rachel to fight for their lives.
Everything hinges on their ability to keep King Cragon from stealing the one item that would allow him to rule Mistasia forever, the Last Emerald.