No two are alike, and that is the first thing those who meet them say. A Brood beast is usually the size of the animal that bore it, with the body plan of its mother and parts of something else: a fox with a wasp’s banded abdomen and a sting where its brush should be; a hare with a beak and a ring of black eyes; a boar covered in feathers that are half scale. Joints bend where joints should not, and some carry limbs they never use. The skin is often too thin, with something visible moving underneath. They make the sounds of several animals at once, a bark that ends in a chirr, and they smell of warm meat and crushed leaves.

They live round the scar of an incursion, in the woods and fields a Bloom reached but did not swallow. Most lines die out within a few generations. The Wrongwood’s are not one unbroken line from the Bloom: its burned ground still holds sleeping spores, and beasts that den on it still bear new Broods, so the woods keep a few however hard the valley below hunts them.

They keep their mothers' habits as far as their bodies allow: a Brood wolf hunts with others of its kind, if it has any, and dens like a wolf. They are always hungry, since their bodies are always growing and changing, and they eat far more than the beast they came from. They are bold with people, and many attack without warning. Some seem to suffer, and to know it.

They carry what their bodies give them, a sting, a beak, a hide too tough for an arrow, and nothing is predictable. The worst is that they breed true to nothing: a Brood litter is as mixed as the first, and a Brood beast may mate with an ordinary animal of its mother’s kind and bring Qzoth’s change into a sound herd or pack. Whether they carry the Bloom’s spores is argued; the safest view, and the common one, is that they do.

Most die young, of bodies that do not work. Those that live mature fast and breed early. Few live long; their bodies keep changing until something fails.

They give nothing, and nobody will eat them. Farmers and foresters below the Wrongwood hunt them with fire and burn the carcasses where they fall, and burn too any ordinary animal that has mated with one, which is the ruin of many a herd. Lords who must deal with them pay for hunting parties and pay more to keep the matter quiet.

Where they are known, people call them "wrong-born" and treat the birth of a malformed calf or lamb as a sign of one. Most such births are only ordinary misfortune, and the burning that follows is cruelty, not caution. Some believe a Brood beast is a punishment on a household that offended the gods; the beasts know nothing of it. What Qzoth is, and whether a Brood can ever breed back to a kind, nobody knows; see Knowledge of the Cosmos.

Beast-hunters who take the valley’s bounty on Brood beasts burn their own boots and spear-hafts afterwards, and the hunter who killed the great wrong-born boar of the Wrongwood’s edge is a hero of the Headwater songs who is said never to have touched his children again.