Reavers are a group of humans in the television series Firefly and the movie Serenity who live on the fringes of civilized space and have become animalistic. Their existence is officially denied by the Alliance, the ruling government of humanity, but they are a harsh reality around the outer planets.

Some believe Reavers are men who travelled to the edge of the star system and were driven mad by the open vastness of space. This theory, reminiscent of a Nietzsche aphorism, has been stated and discussed between most of the crew members of Serenity. Shepherd Book believes that they are "just men" who have been removed from civilization far too long, men who could be helped. Jayne and Mal strongly disagree with the Shepherd's opinion. The Reavers' true origin is revealed later in the movie Serenity.

BEHAVIOR
Reavers are savage, brutal and primal. Their contact with other humans appears limited to combat, rape, torture, murder, and cannibalism, and no dialogue has ever been shown; yet they are never shown in conflict with each other. They are still able to cooperate and act purposefully enough to use spaceships and set highly technological traps, suggesting that they have retained some level of higher intelligence.

Reavers are known to raid ships and colonies to rape, cannibalize, skin, and kill, anyone they find (not necessarily in that order). They growl and snarl like beasts, and their methods are considered so horrifying that, when faced with capture, victims have been known to attempt suicide, and mercy killings of those who fall into the hands of Reavers are considered humane. The Reavers do occasionally intentionally leave survivors of their raids, but they drive these survivors mad through forcing them to watch the torture of those they were with, effectively turning them into second-hand Reavers. The Reavers also severely mutilate themselves (i.e., by cutting themselves, peeling off their skin, and/or sticking bits of metal into their flesh).

They live in macabre ships stained with blood and decorated with corpses chained to the hulls. Seemingly, they live their whole lives in space, only touching down on a planet or moon to raid whoever lives there.

TECHNOLOGY
Reaver ships, captured from their victims, are instantly recognizable by the haphazard red stripes and bodies of victims adorning their hulls. They are also known for "running hot": without proper engine radiation containment, a practice tantamount to suicide. This makes Reaver ships significantly faster than their normal counterparts, but also makes it easier for their prey to detect their arrival and to hide by powering down their ships rather than fleeing. The Reavers' habit of ramming their victims with indifference to damaging their own hulls, tends to leave their ships appearing battered or torn. Their craft possess a wide variety of exotic weaponry, many of which are designed to snare and capture other ships including harpoon cannons, grappling lines, and energy nets. They utilise weapons which fire giant sharpened disks similar to buzzsaws or shuriken, in addition to more traditional anti-ship ordnance. Reavers will use any sharp object as a weapon in hand-to-hand combat. To cripple rescue ships, they have been known to leave a bait ship intact with a distress beacon. When a passing ship docks to aid them, a bomb detonates when the ships disconnect, destroying the already derelict ship and crippling the ship that tried to provide aid.

DESIGN
Comic book artist Bernie Wrightson, co-creator of Swamp Thing, contributed Reaver concept designs for the film Serenity.

ORIGIN
In the movie Serenity, Reavers are revealed to be humans from the planet Miranda. The Alliance government on Miranda added a chemical agent known as G-23 Paxilon Hydrochlorate, or simply "Pax" (Latin for "peace"), to the planet's air processors. The Pax was supposed to calm the population and weed out aggression. The agent worked, but too well: 99.9% of the population became so lethargic that they stopped working, breeding, talking, and eventually eating and breathing. They lay down where they stood and allowed themselves to die. The remaining 0.1% of the planet's 30 million people (roughly 30,000) had the opposite reaction to the Pax. Their "aggressor response" increased beyond madness, and they became mindlessly violent and aggressive without limit. They killed all of the government officials that remained on Miranda, and then broke into the laboratories to torture and eat the scientists. They then left the planet, where they developed into the savage sub-race of the Reavers.

In the climax of the film, a massive space battle between the Alliance and the Reavers occurs, and it is implied that the Alliance fleet wins the battle. It is unclear exactly how many Reavers participated in the battle, but it can be assumed that many of their number were destroyed.