Cleon
Legend
Great idea!
Updated.
Organization: Solitary or x (2–4) [x="paradox"? "countdown"? "pack"?]
Challenge Rating: 5? They are roughly the equivalent of a wraith
Advancement: 5-12 HD (Medium)?
Temporal stalkers speak Common and Draconic? (Draconic is the closest thing to an ancient language)
That all looks good to me, except for a couple of points.
Firstly, there's a minor error in the stats: Speed: Fly 50 ft. (perfect) (6 squares) when it should be 10 squares.
Secondly, I'm not terribly fond of "countdown" as a collective noun.
Maybe an anachronism of Temporal Stalkers?