Weeping Angels

The Weeping Angels (Also known as the Lonely Assassins) are an extremely powerful race of Quantum-Locked humanoids which first appear in the fourth episode of Season 1, so called because their unique nature necessitates that they often cover their faces with their hands to prevent trapping each other in their petrified forms for eternity by looking at each other, thus giving them their distinct "weeping" appearance. They are known for being "kind" in the sense that they normally kill their victims by sending them into the past and letting them live out their lives, just in a different time period. In turn, this allows them to feast on the remaining time energy of the victim's life. However, when this energy source pales in comparison to an alternative power source, they are known to break their victims' necks.