John Dee was an astronomer, spy, magician, and confidante to Queen Elizabeth I. According to the Sixth Doctor, he was a man of both science and superstition. (PROSE: Mortlake)
The Sixth Doctor and Evelyn Smythe met Dee in 1568 at his mother's home in Mortlake. Using an incantation in The Steganographia, Dee summoned Padiel, a hyper-intelligent communications avatar used by the inhabitants of Sintra. The Doctor convinced Dee his ritual hadn't worked, and swapped the book for one with a harmless version of the incantation. Later, Evelyn wrote a book about Dee, The Merlin of Mortlake: The Life and Talents of Dr John Dee. (PROSE: Mortlake)
To resolve a temporal paradox, the Seventh Doctor and Ace kidnapped John Dee and Edward Kelley in 1568 and left them in 848983. There, Dee and Kelley worked for Uriel to create an SOS using the abandoned streets of Prague. In 848988, earlier versions of the Doctor and Ace saw the SOS and came to the rescue. Uriel took the TARDIS, forcing the Doctor and Ace out with Dee and Kelley in 848983. Shortly, the older Doctor and Ace arrived and swapped out the older Dee and Kelley for the younger versions, then brought the older versions back to 1568. (PROSE: Sunday Afternoon, AD 848,988)
The Sixth Doctor and Peri met Dee in 1572. (PROSE: A Handful of Stardust)
Dee, a master of espionage, founded the British secret service with Francis Walsingham. (PROSE: Newtons Sleep) He used the bizarre cryptographic Enochian language in experiments to brainwash agents through communication with angels and demons, and he developed an occult scrying ritual. His personal code number was 007. He entrusted the five secret names of the Points of the Star to the Service. At the time of founding the Service, he wrote of a mythical arch-nemesis known as "Chroronzon", a demon depicted in occult lore as a gigantic eye. (PROSE: The Adventuress of Henrietta Street)
After being forced to flee Britain, Elizabeth's personal astrologer convinced the Holy Roman Emperor that he could transform metals into gold and create homunculi driven by captured angels or demons. His notes only survived as third-generation copies, which as the The Gazetteer remarked, made "little sense even by ritual standards." (PROSE: Bêtes Noires & Dark Horses)
According to one source, Dee was actually the immortal Jared Khan, who was hunting the Seventh Doctor. (PROSE: Birthright)
James I concluded the Thirteenth Doctor was a witch because she was named after the necromancer "Doctor Dee". (TV: The Witchfinders)