You will need a F.E.A.R. Combat CD Key to play this game. You can get them free from the official site.

F.E.A.R. Combat includes all the updates, all the new official maps and the new official modes released for F.E.A.R. Multiplayer in one downloadable file. F.E.A.R. Combat users will be able to play against the owners of the retail version of F.E.A.R. as well as the other F.E.A.R. Combat users.