From fattwiki

Weavers are tree-like humanoids with long, spindly bodies and limbs. Their flexible and oddly shaped bodies are uniquely suited to a number of tasks, although some people find their appearance creepy. Without adequate access to water, they grow weak and brittle, and must retreat into the soil.

They have been known to live in the forest southwest of Marielda, in Marielda proper, and (post-Erasure) in Old Man's Chin.

The first weavers appeared in Marielda during "The City of Light Pt. 1". Hedy Braum was the first of many to disappear in the Marieldan woods and be replaced by a weaver who looked like her (who was found in a tree and brought back to the city). Other weavers soon followed. The discovery of the human Hedy's corpse confirmed that the weavers were not the same beings who were originally lost to the woods. The weavers fought the forces of Samot during the Quiet Year, but as they were considered disturbing they often worked in dangerous and unsafe conditions, and eventually formed the Weaver Union to protect themselves and band together with other vulnerable people.

Some weavers in Old Man's Chin have formed a weaver king, a mass of fused weavers with extraordinary abilities, but it is unknown how common this is. Other singleton weavers remain buried under the snow and earth, reliant on the weaver king for hydration. They are described as particularly plantlike in a way that was later used to retroactively describe the young Marieldan weaver Edilia Rosamund, who has rosewood bark which grows patches of flowers.