Shadow ghosts, dark entities:

[Chronos]

These ghosts usually appear as a shadow of sorts. They look a bit like Ecto-mist but with form and are normally reported to be two feet in length or longer and tend to travel at a height of two to ten feet. In photographs it's easy to confuse them with natural shadows so be careful. They are usually sneaky and evasive. When they are spotted it's usually out of the corner of your eye or as they are darting through a wall. They are often spotted in a mirror as well.