Solitaire Legends: Guinevere

From BoardGameGeek:

Morgan le fay hast placed a curse over Camelot! There art four Arthurs seated at the round table. Three art changelings who've stolen the king's true form. Guinevere must find Merlin's crystals and send the imposters back to the faerie realm. But maketh haste, for the fabled knights art under the witch's spell and seek to destroyeth thee!