A chimera is any object, animate or inanimate, from the Dreaming, or made of the essence of the Dreaming. In practical use, "chimera" refers to an animate and likely sentient creature of the Dreaming, while an inanimate object would be referred to as "chimerical" (e.g. a chimerical sword). Even so, an inanimate object from the dreaming is still technically a chimera. It is unclear what is formally a chimera and what is not as one progressed deeper into the Dreaming. By technical definition, anything that exists in the Dreaming that is not fae or an exotic material (such as a visiting mage) would be a chimera, down to every last blade of grass, grain of sand, and particle of dust.
Chimera are generally visible only to those who can see into the Dreaming, and are highly susceptible to Banality. They possess a sort of magic called redes. Redes are given as a hodge-podge of powers to a chimera using a specific point-based system, or by the Storyteller. Some redes include the ability to deal aggravated damage, or to become Wyrd for a time.