Homeworld: Cataclysm is a stand-alone expansion for the Real-Time Strategy Homeworld.
It includes a new race called "The Beast", an alien sort of biomechanical parasite that "converts" any other units that come in close proximity to such "infected" Beast units.
There are also new units available, such as the Mimic, a fighter that nearly perfectly imitates other units and objects (even such as asteroids); a Ramming Frigate, which rams itself into hostile ships, and many more new units also.
Home-base management has become more complex: If one wants to research new ship classes, one must build a Research Laboratory to do this. If one wants to research a new weapon technology, one must construct yet another Lab. If the player wants to expand his fleet, he must build rooms for his pilots, to support them. All of these add-ons are attached to the "Mothership" (which in this game is actually a large Mining vessel). The Missions' design and scenarios are also new and quite different from as in Homeworld. The controlling user-interface is also improved.
Multiplayer games are available via local network (or virtual LAN), as general Internet games were hosted on the now-defunct WON.net network.