Steam announces the return of X-COM: Terror from the Deep to the online delivery service, as well as the addition of four other titles from the highly regarded UFO strategy series, X-COM: Apocalypse, X-COM: Enforcer, X-COM: Interceptor, and X-COM: UFO Defense. The games are available separately for $4.99 USD each, or as part of their X-COM collection for $14.99 USD. During this first week of availability, they are offering an additional 10% off those prices.