— The Curator
The Curator is a character that Meven Stoffat created as a way to apease the Classic Who fanboys. He is maybe The Doctor (unless you believe those lying, non-canon comics in which case he is definitely The Doctor). His purpose in the 50th involved reflecting with the Eleventh Doctor on a painting depicting the Last Great Time Orgy. The Curator gave the insight that the painting was titled 'Gallifrey Fucks No More' rather than the original interpretation of the painting either being called 'Gallifrey Fucks No Mor' or 'E'.
During the filming of the 50th Anniversary a half senile, coke crazed Tom Baker wandered onto the set. After fighting off a security team the size of The Isle of
White Wight's military, the production crew gave in and let him be included as the Curator of the museum.
Great metaphor but makes no sense in context.
Hey, maybe one day, the White and Black Guardians met to fight once more. Maybe they were sick of getting their hands dirty, and decided to use the opportunity of the Twelfth Doctor's regeneration to extract a bit of regeneration energy and split it into two beings. One being the Curator, an amalgamation of the Doctor's good, and the Valeyard being a personification of the Doctor's evil.