Resources and style are maintained differently between the three different races of playables.
Humans gain credits by repairing atmospheric generators with their engineers. These generators produce a steady run of credits until they finally break down. They also gain credits by killing their enemies. The Comm Tech can call in additional reinforcements into beacon sites on the map, these are deployed from a dropship.
Predators must hunt their prey and take their heads as trophies to gain more points. They are the more expensive faction to maintain and possess a large number of upgrade better vision modes. The predator shrine is their HQ unit which is mobile and contains heat beams for defense. They also allow the summoning of new predator units which are deployed by drop-pods anywhere visible though cannot be dropped into caves for obvious reasons.
The aliens are the more different in managements for they gain infestation points for every enemy unit that is implanted by a face hugger. The face hugger themselves are created by the Alien Queen which constantly produces eggs. As such, the Queen is vital to the survival of the colony and is a powerhouse in combat. The queen has to remain stationary to create an ovipositor which creates the eggs and in this state is vulnerable to attack.
Unlike strategy games, Extinction has no concept of infrastructure as everything is mobile. There is a population cap that only allows a set number of units in the game and the only form of 'fixed' structures can be moved or are defensive. These include human sentry guns, alien hive nodes and predator mobile guns. The units also make heavy use of upgrades and special abilities to further enhance the units in battle.
Predator plot[edit]
The Predator campaign initially involves encountering humans and aliens but also involves fights with computer controlled predators. The story premise is that the Ancients, who are the oldest and the leaders of the predators, are determining which is the best hunting tribe. The victor then is awarded the right to use the military predators who are far more powerful. After five skull hunts, the sixth mission assigned is to terminate a predator who willingly surrendered to the humans and to capture a human researcher involved. In the end, the predators find out that the humans have been attempting to create their own version of the aliens called the 'K-Series' - a 'yellow' breed that eventually escapes. The head researcher also was capable of mixing the genetic material of predators and aliens creating a Predalien Queen. The predators' final task is to destroy this hive, then use a thermonuclear device set by one of the Ancients (the mission fails if he dies before the task is complete).
Alien plot[edit]
The Alien campaign involves the alien colony awakening from its hibernation within a cave complex which has humans invading it. The colony infects the human trespassers and escapes the caves which are then targeted by the marines, destroying it. The Queen then escapes to a tropical environment, where the hive encounters Predators. While this is happening, the human scientists capture some of the aliens and attempt to breed their own species, creating a new 'yellow' alien faction called the 'K-Series'. Testing of this new species involves its destruction by the 'pure breed' aliens who do not tolerate genetic changes. This splinter colony of the pure breed aliens is eventually set free when a predator strike team attacks the human installation and escape with the head researcher. After their escape, the splinter colony's queen is captured by predators, and the aliens free her. The final mission involves the aliens fighting not only the predators and humans but the 'yellow' alien faction which has managed to survive, to cleanse their race.
Marine plot[edit]
The Marine campaign involves Beta Unit a squad of elite marines to wipe out all threats to the local human population. The marines then come across an unidentified object that attacks them. The marines win, but learn of two more devices that were made to cloak a predator base on the planet. The marines are also assigned to assist Dr. Kadinsky's alien project by retrieving two alien eggs and a praetorian in a royal cocoon. Once the cloaking devices have been destroyed, five predator anti aircraft turrets must be destroyed before assaulting the predator base. Along the way, hostile humans try to stop and kill the marines (they are thought to be bounty hunters) throughout certain levels. The final mission involves finding Dr. Kadinsky in the predator base, who is dead, destroying an entire alien hive, and using an enhanced synthetic to place a powerful bomb.