Never have I ever thought the Master of Masters was a real person. Don't believe me? The evidence is in the links below.
https://twitter.com/RayChase/status/904483172708208641
https://twitter.com/RayChase/status/904721180078329857
https://twitter.com/RayChase/status/904773896095838208
https://twitter.com/RayChase/status/904789852092289024
Edit: He was looking up spoilers for KH3 in the Book of Prophecies! That tease!