Time beetle
From Tardis Wiki, the free Doctor Who reference
A Time Beetle was a being capable of manipulating time. It was used by, or was part of the Trickster's Brigade. With the help of humans within the brigade it was attached to unsuspecting victims, after which it changed a key event in their lives.
Time beetles were invisible to humans, except to some extra sensitive ones, in times where the difference between the normal and new timeline was unusually great. (DW: Turn Left)
