The Dream Lord

The Dream Lord was the dark side of the Doctor, who seems to have control over dreams. He was created by speck of psychic pollen from the candle meadows of Karass Don Slava that had gotten stuck in the TARDIS, and awoken as it was warmed up. The Dream Lord was created by the pollen from the Doctor's inner darkness. He trapped the Doctor, Amy Pond and Rory Williams between two dream worlds, telling them they would have to choose between them. However, the Doctor eventually realised that both weren't real, and managed to return them all to the waking world. After removing the pollen, the Doctor saw the Dream Lord's face in his reflection in the TARDIS console, smiling slyly at him. (DW: Amy's Choice)