Midnight entity

The Midnight entity is some sort of extraterrestrial lifeform of unknown origins found on the planet Midnight. It is one of the few beings that the Doctor has no knowledge of at all, which, given his expansive, encyclopedic knowledge of the universe and everything in it across time, is a testament to its obscurity. The creature is never given a name, nor does it reveal its true form, making it perhaps the most mysterious of all the enemies he has faced.

Powers and Abilities

 * The full extent of the entity's power is unknown. Indeed, it is unknown exactly how many of the events in the episode the entity was directly responsible for. It is also unknown whether the entity is part of a species, or existed alone on the planet.

The Midnight entity was capable of surviving on the planet Midnight, despite the fact that the Xtonic rays should kill it. It was capable of shaking a Crusader 50 bus, causing dents in its walls and ripping off the front section.

The Midnight entity could also possess a human without entering. It would start to copy what the people around it said, then speak at the same time and then predict what people would say. The Doctor believed it was trying to learn about its surroundings. The being seemed to be able to learn at an incredibly rapid pace and absorbed the passengers’ speech without forgetting, hesitating, or making a single mistake. After singling out the Doctor as a target, the entity was able to paralyze him and force him to repeat the entity's speech. (DW: Midnight)


 * The paranoia that the passengers experienced may have been caused by the entity (as it suggested) or may have been a case of mass hysteria.

History
During the Crusader Tours to the Sapphire Waterfall, the strange entity attacked a tour bus. The entity at first knocked on the Shuttle and then, when it had found a host, somehow made it inside the shuttle without any sign of a hole in the vehicle. It choose to possess Sky Silvestry. The entity seemed to gather the strength of its host and then repeated every word a person said in exact precisions, including the square root of Pi in 30 decimal places. Eventually, the entity copied word-for-word at the exact same time, focusing on the Doctor's voice, and eventually stealing his voice. She convinced the rest of the crew to try to throw the Doctor off the bus, convincing them that he was now possessed, but the Hostess threw herself and Sky off the shuttle to save everyone.

Despite this, the Doctor had no idea if this killed the entity or if there were more. (DW: Midnight)


 * It is also unknown what the creature's ultimate intentions were as it never really got a chance to speak on its own. It was most likely hostile, as it wanted to have the Doctor thrown out into the sun. It preferred the bodies of corporeal creatures to its native environment, as the entity said the environment was cold and dark. It seemed to take some form of pleasure in the heat, blood, and pain of living corperal beings.

The entity within Sky also said (more to itself than the others, since at the time they were busy dragging the paralyzed Doctor to the hatch) that "that's how he [itself] does it--makes you fight," indicating that the xenophobia and paranoia was at least partially caused by the creature, for unclear reasons. The rest of the passengers seem to immediately relax once Sky and the Hostess have been dragged outside, though this might have been merely of the shock of seeing the two of them die.

Behind the Scenes

 * This is the first time on Doctor Who where the true nature of an enemy has never been revealed. The name of the creature is not revealed in the episode, and "Midnight entity" is just an unofficial name.
 * The entity seems almost identical to the species in the Doctor Who Unbound audio drama A Storm of Angels, right down to the gemstone planet it inhabited; since DWU features stories taking place in alternate realities, this might well be that reality's version of the entity and Midnight itself.
 * The entity seems to have once possessed a physical form, before becoming incorporeal. It also seems to have a vested hatred for the Doctor, not only singling him out but taking considerable pleasure in trying to have him killed, even though the Doctor is the only one of the passengers who wanted to help the Midnight Entity and protect it from the other passengers. Whether this means the entity is someone or something that has encountered the Doctor before, when it had physical form, is unknown.
 * One of the more intriguing things of all is that the entity briefly refers to itself as 'he', saying, "He's waited so long, in the dark, the cold, and the diamonds."  Theory: This could be a reference to The Master's apperance in Utopia/The Sound of Drums/Last of the Time Lords. As Utopia was referred as "The dark and the cold." but was said to have "skies made of diamonds." These descriptions would not have been heard if The Master had not returned.