Arrow of Time

Origins
The Arrow of Time is one of the oldest artifacts, being created along side time itself (or at least that what the senior agents tell the newbies). In Greece, a mortal got his hands on it and was taken as the Titan Chronos until the power of time overwhelmed him and erased him from time.

Arthur Eddington was the first person to be able to study it, but the arrow thought that time needed to move on, so it left, leaving him only with his theories.

Effects
The Arrow requires being constantly moving forward, so storage has always been an issue, usually it wound up in a wind tunnel of sorts. When disturbed though, it will have a devastating effect that is unpredictable, ranging from time travel to immortality to becoming frozen in time to being wiped from the timeline.