10. He's A Natural Extension Of The Dream LordBack in the series 5 episode Amy's Choice, we saw the Doctor come face-to-face with his dark side in the persona of the Dream Lord. Some psychic pollen got trapped in the TARDIS's time rotor and allowed the Doctor's inner darkness to achieve a partial manifestation. He didn't have a physical appearance, but he was real enough to torment the Doctor, Amy, and Rory with his mind games. When his episode aired, he immediately drew comparison to the Valeyard. The similarities were undeniable, and several people put forth the opinion that the Dream Lord was an early stage in the Valeyard's development, a point when he wasn't yet strong enough to achieve a separate physical appearance. The episode's ending even hinted that we might see the Dream Lord again at some point--after all, if he is part of the Doctor, he can never truly be defeated. Moffat stated that he wasn't going to be bringing any of Matt Smith's storylines over into Peter Capaldi's run as the Doctor, so whether we would actually see the Dream Lord is debatable. However, the Valeyard's storyline is an older one, and tying him with the Dream Lord would be a neat connection of old and new Who.