"doctor Who" Heaven Sent(2015) -

: A creature manifested from the Doctor's childhood nightmares. It only moves when the Doctor is not looking or when he stops confessing.

: Appears only as a manifestation of the Doctor's imagination, providing the motivation he needs to keep fighting through the cycle. Cultural Impact & Critical Reception "Doctor Who" Heaven Sent(2015)

The episode received universal acclaim and remains a high-water mark for the series: : A creature manifested from the Doctor's childhood