The Harbinger, which was once a census ship is now a vessel bent on wreaking chaos through the solar system. The objective of the vessel is to dominate any unexplored territories of the universe and abuse all that oppose this goal. In these territories lie civilizations whose survivors are taken up into ship for study in laboratories that involve malicious experiments. Unlucky survivors are also seen being taken into labor camps. The game begins in a setting where "the lucky” of the survivors must escape into the deep and forgotten crevices of the ship. Here, it is where the underground society is developed and where members of this society struggle to survive off whatever they can find. This conflict, coupled with the fact that many high-alert patrols are sent out to find these survivors makes life on the ship Harbinger especially difficult.

Harbinger is not a sequel but rather an original release. Unlike Diablo 2, this game offers no multiplayer game play or online capabilities. This game is limited to single player mode in which an individual must choose from three distinct races. Harbinger is a game that is set in space but more specifically it is set on a centuries-old human ship, which at first began as a census vessel. The Harbinger, which is planet-sized, is filled with various creatures and other inhabitants. The main conflict arises when enormous bug-like aliens begin to wreak havoc on the ship. These large aliens are known as Cimicidae. The Cimicidae are not the only troublemakers on this ship; The Vantir and Scintilla are the last of the three races of enemies one must face in this game. The Vantir are an opportunistic and very old race that seeks to dominate the ship through the use of power suits and advanced weapon technology. The Scintilla are a tribal race that have the ability to harness the energy around them appear thin and leathery.

The three major races on board the Harbinger are the human male, culibine female, and gladiator male. All the character races are presented with their own unique style of offense and defense. The human male is able to boost his speed, use injections to restore health, wear armor, and use both a melee (blades) and non-melee (gun) offense. The culibine female is unique in the fact that she is unable to attack in a melee mode but is able to utilize drones to help on her offense and defense. What the culibine female lacks in strength she makes up for in speed and agility. The gladiator male is a cyborg, more specifically a robot that has had a human mind transferred into its core.

The gladiator male is able to attack with a cannon and melee style blades while being protected by a stronger armored torso. The gladiator male also utilized robots called "cams'. Even though he may sound like your best choice, the gladiator male is extremely slow and sometimes cumbersome. Each character is endowed with special skills that are at the same time balanced in a way where no one group/race is easier or harder. Also, the designers of the game made the weapons more effective on certain races, for example cyborgs would be more affected by electromagnetic pulse attacks. Conversely, the aliens would be less affected by these pulses and more susceptible to different forms of attack. This concept of using varying weapons with different degrees of effectiveness adds to the general variety of the gameplay but Harbinger is simply redoing what has already been done.