Rather than a specific race, The Silence are a religious order. Their agents on Earth have been there since before the dawn of mankind, directing human evolution. Through the use post-hypnotic suggestion, The Silence make people who see them instantly forget their existence.
"The Waters of Mars" is the third episode of the 2008–2010 specials of British science fiction television series Doctor Who, broadcast on BBC One on 15 November 2009. It aired on BBC America on 19 December 2009 and was released on DVD and Blu-ray in the UK on 11 January 2010 and in the US on 2 February 2010.
The creature in Midnight is more than just this idea, it has to have a physical form as well (or should, since they saw shadows moving outside the bus). The question is what is the name of the physical manifestation of this idea that you are saying it represents.
The Doctor didn't know whether the Boneless entered his universe to invade, infiltrate or just to "replace" humanity, but he believed that the role they "seem[ed] determined to play" was that of "monsters", and with him being "the man that stops the monsters", it was his duty to defeat them.
Known as “The Lonely Assassins”, the Weeping Angels are quantum-locked alien killers, as old as the universe itself. Little is known of their origins or culture. When observed, they freeze like stone, but in the blink of an eye they can move vast distances.