Sutekh
The One Who Waits was an individual active in the Doctor's universe, whom the Doctor themself was unfamiliar with.
Biography
Once the Toymaker managed to escape into the universe, he found the One Who Waits "hiding". Whilst the Toymaker had bested the Guardians of Time and Space, the dying Spy Master and "God", he opted to flee rather than challenge the One Who Waits to a game. He later told the Fourteenth Doctor of his decision to flee from the One Who Waits, with whom the Doctor was not familiar, (TV: The Giggle [+]Loading...["The Giggle (TV story)"]) something the Toymaker found "hilarious". The Toymaker thus decided not to spoil the surprise, (PROSE: The Giggle [+]Loading...["The Giggle (novelisation)"]) instead cryptically telling the Doctor it was "someone else's game." (TV: The Giggle [+]Loading...["The Giggle (TV story)"])
References
In his novelisation of his battle with the Doctor, the Toymaker promised the Doctor's inevitable encounter with The One Who Waits would be novelised as Doctor Who and the I'm Not Going to Tell You. (PROSE: The Giggle [+]Loading...["The Giggle (novelisation)"])
