The Eater, also known as the Ultimata, is a sentient black hole that arrived in the Sol System in 2023. It is the primary antagonist of the 2000 novel Eater.
The core of the Eater system is a micro black hole, a meter or two in diameter and massing about as much as Luna. The black hole's ergosphere is about ten meters across.
Outside the black hole is an accretion disk much larger, though far less massive, than the hole itself. The disk consists of superheated, compressed dust and plasma being consumed by the black hole. Two empty "funnels" point away from the black hole's poles, through which the Eater can direct jets of plasma. The accretion disk region also contains the black hole's magnetosphere, where its intelligence resides in the form of waves. Because the Eater's mind is in the magnetosphere rather than the black hole itself, it is not invincible, and could theoretically be killed with a strong enough disruption to its fields.
The Eater can feed off any kind of matter. It usually feeds on small objects such as asteroids, ionizing them with its jets before eating the resulting plasma. This matter is used to propel and sustain the black hole system.
The origin of the Eater's black hole is unknown, even to the Eater itself. It speculates that the black hole is a supernova remnant, although given its size it is more likely that it is a primordial black hole formed during the Big Bang. In any case, this black hole remained an inanimate celestial body until 7.5 billion years ago, when it collided with a planet inhabited by a civilization that the Eater terms "the Old Ones." The collision destroyed the planet, but the Old One civilization uploaded itself into the black hole's magnetosphere, creating the Eater entity.
After this, the Eater began traveling around the Milky Way galaxy, seeking out other intelligences to learn from. Among the beings it encountered were a race of fast-thinking clay-based organisms and an enormous, sentient cloud of gas. The Eater eventually began to desire "companionship" and began slaking its desire for knowledge and company by forcibly adding sentient minds to its magnetosphere. By the time the Eater arrived in the Sol System, it had perfected a method of acquiring these minds; it would demand that civilizations convert the minds of selected citizens into digital form and beam them to it in microwave transmissions. The Eater would lay waste to civilizations that refused to comply.