|For other uses, see 0-8-4 (disambiguation)|
An 0-8-4 is a term used by S.H.I.E.L.D. to denote an object of unknown origin. Depending on the situation, either a small or large group of agents are sent to determine what the 0-8-4 is, and how it could be used.
The code "0-8-4" derives from the identification number used on the case containing the first object of unknown origin, as it was the eighty-fourth item catalogued. The object was a Diviner obtained by the Strategic Scientific Reserve, the precursor of S.H.I.E.L.D., during the raid of the HYDRA Research Facility in Austria in 1945.
Leo Fitz explained to Skye that he had never experienced an 0-8-4 being a person, though it was possible. He elaborated by saying that he has read about weapons, spacecrafts, and energy sources labeled as 0-8-4s, citing that the only characteristic they had in common is that all were dangerous.