The Killers are a highly aggressive species or faction of aliens that deploy fleets of self-replicating machines to destroy inhabited planets. They are the main antagonists of The Forge of God and Anvil of Stars.
Over 400 different species of intelligent life forms inhabit the Killer home worlds in the Leviathan System. It is never made clear if these species are true Killers, unaffiliated life forms created as "human" shields, or simply biological constructs controlled by the Killers to maintain a ruse of a peaceful civilization. The minds of these creatures are not limited to one body and usually control many bodies simultaneously. If the sole specimen sent to Earth is any indication, the internal anatomy of these species indicates that they are artificial and not designed for long lifespans; in fact, waste material simply builds up in their tissues. This specimen also acted deliberately to destabilize Earth's defenses as the Killers prepared the Earth's destruction, possibly an indicator that all the Leviathan system species are simply manifestations of the Killers.
A species of energy beings called "staircase gods" dwells in the core of the Leviathan system's fourth planet, Sleep. The other Leviathan races claim that the staircase gods created them, although the staircase gods deny this. The staircase gods also claim to be direct descendants of the Killers, but innocent of their crimes. Given the Killers' great skill at misdirection, however, it is likely that the Killers include at the very least the staircase gods, and possibly the Leviathan system's entire population.
The Killers' origins are unknown, although they probably evolved in the Leviathan system. At an unknown point they began destroying inhabited planets, and thus became a target of the Benefactors. They attacked and decimated the Red Tree Runners in around 2,000 BCE, but did not succeed in destroying them or their home planets.
Killer technology is roughly on par with that of the Benefactors, and appears to exceed it in some areas. Most of this technology is geared either toward their own defense or the genocide of other species.
Much of Killer technology relies on "noach" or "no-channel" science. Noach manipulates the connections of quantum entanglement between particles and points of space, allowing the creation of "fake" matter and the manipulation of the fundamental properties of particles. The Killers can convert matter into antimatter and create fake matter with substance but no mass, even on the scale of whole planets. Eleven of the fifteen planets in the Killers' native Leviathan system were fake matter constructs made in this way. One of the other four, their apparent "capital" of Sleep, was originally a small star until it was heavily modified into an impossibly large terrestrial planet.
The Killers use self-replicating machines to destroy other planets rather than going themselves. These machines resemble needles 50 to 100 meters in length, and replicate using material found in the target system. They manufacture neutronium and antineutronium and send one mass of each material at the target planet, causing them to annihilate in the core and blow the planet apart.