Dr. John Dee is the main antagonist of the book series The Secrets of the Immortal Nicholas Flamel by Michael Scott. He is based on the alchemist and mathematician from history, however in the book he has actual magic powers and is immortal, still living even in our modern age.
John Dee has been an enemy of Nicholas and Perenelle Flamel since their time in the Sixteenth Century. He had always chased them to get the Codex for his masters, Isis and Osiris, but he didn't get it until they had finally found the legendary twins, Josh and Sophie Newman, they had searched for all the time.
Working together with Niccolò Machiavelli he succeeded in bringing Josh on his side, but after being declared "utalga", he turned against his masters. In the end, he eventually redeemed himself by dying for the triumph of Josh and Sophie in the battle of Danu Talis. ]