Trickster God

One of the Sun Builders worshipped as gods by the Gendar was a Trickster God of many names. He was said to be "the worst of the lot", though having "his heroic moments" as well in some myths. After finding his seal scrolled on one of Box's memory boards, Maxie Masters came to believe that he had been the same time traveller who built Box and gave her to P.R.O.B.E.. (PROSE: Out of the Box)

Behind the scenes
The clear suggestion is that this Trickster God figure is Gendar mythology's echo of the Doctor.