The Secret of the Swamp King by Jonathan Rogers

Back Cover: Your majesty – I write to warn you: your most dangerous enemy dwells under your roof.  Beware the youngest son of Errol. He has convinced himself that he is the Wilderking of ancient prophecy, and the rightful occupant of the throne at Tambluff.  His every action is calculated to convince your courtiers of the same…he shamelessly claims to be friends with the feechiefolk, part of a scheme to build a legend around himself that is in keeping with the Wilderking Prophecy. Your majesty, it pains me to accuse a fellow Corenwalder of treason. But it pains me more to think that my king would be nurturing a traitor under his own roof. Yours sincerely, A loyal subject”