Dream Lord
The Dream Lord appeared in the Series 5 episode, Amy’s Choice (Series 5 : Episode 7) as the main nemesis of the episode. The Dream Lord has trapped the Doctor, Amy and Rory in two realities, a Leadworth reality where Amy and Rory are married and expecting a child, and a TARDIS reality, where the Doctor, Amy and Rory are trapped in a broken TARDIS that is heading towards a cold star that will kill them. The Dream Lord has control over people’s dreams and when they sleep, routinely sending the trio to sleep in one of the two realities, forcing them to wake up in the other. He said he had set up a test, in which they faced danger in both realities but they had to chose which one was real, and which one was false.
The Dream Lord taunts the Doctor on his own insecurities and pressures Amy into assessing her dreams for the future, whether she wants to settle down with Rory or continue adventuring with the Doctor. The Dream Lord appears in both realities to speak with the trio to make them chose a reality, however the Doctor works out that both realities have been falsely created by the Dream Lord, who is revealed to be a darker side of the Doctor himself. The trio wake up in the Doctor’s real TARDIS safe and sound, where upon the Doctor explains that specks of psychic pollen from the Candle Meadows of Karass Don Slava had got caught in the TARDIS and induced a collected dream state between them all. The Dream Lord appeared in a reflection of the Doctor after they had all woken up, indicating that he is still there, waiting and hiding within the Doctor.