The games are, for the most part, individual pieces of one grand plot, rather than stand-alone stories. It's a very complicated universe, but here are the basics.
Far in the future, humans have invented faster-than-light space travel, which has allowed them to colonize other planets. When the outer colonies come under attack from a coalition of hyper-religious aliens called the Covenant, a group of military humans including the supersoldier Master Chief and the AI Cortana accidentally stumble across a giant ring called a Halo, big enough to support life on its surface. The pursuing Covenant disable the human ship, and both groups land on the surface of the Halo.
Master Chief, with Cortana downloaded into his electronic armor, discovers that this Halo is one of many Halos throughout the galaxy, and that they were created thousands of years ago by a now-extinct ancient species called the Forerunners as weapons against insect-like parasites called the Flood. Except Halo doesn't just kill the Flood——it wipes out all sentient life in the galaxy, thus depriving the carnivorous Flood of their food source. The Halo is designed to send out the seeds of life for all of the species it destroys, so that thousands of years later, once the threat from the Flood has passed, life may return. It’s sort of a reset button for the Milky Way.
The Halos have been activated before, and they worked as planned. The humans in the game are actually on their second evolution. The Forerunners, however, never returned.
On the surface of the Halo, the Covenant soldiers are super excited because they worship the Forerunners as gods, and they see the Halo as a holy relic. They think that by activating it they will become enlightened. Master Chief, realizing the destructive power of the Halos, knows he has to destroy them in order to save both humanity and the Covenant.
While running around on the surface of the Halo, the Covenant accidentally release a few surviving Flood, who had been preserved within the Halo. The Flood proceed to infect both humans and Covenants, turning them into a zombie-like army of death.
Master Chief manages to destroy the first Halo, and the next several games detail various wars between the humans, the Covenant, and the Flood, including the destruction of more Halo installations and most of the continent of Africa.
Though the aliens that make up the Covenant have little characterization in the first Halo game, later games go so far as to cast aliens as main characters, giving them distinctive voices and personalities. During the second Halo game, one species from the Covenant realizes that activating the Halos is a really bad idea, and they join with the humans.
4 / 5
3 / 5
2 / 5
0 / 5
