King Philip III is a character in the non-canonical novel, The Queen's Curse.
The King rules the land of Tarsina with pride alongside his wife and son. On the day of his son's wedding day as well as birthday, the queen makes a murder attempt to stop him from putting the country's curse to rest. It is then they realize the queen is actually a loyalist to the curse, one of many who despise the non-magical denizens and strive to make the curse come true to keep the kingdom "clean".
By joining their magic, they manage to wipe the curse from existence, saving the kingdom once and for all.
King Philip III has appeared in a total of 1 episode throughout the course of the franchise.