Made out of whatever the Keeper has on hand, with a piece of the changeling's shadow, a Fetch is a duplicate of said-changeling prior to their time in Arcadia. Sometimes these doppelgangers are absolutely perfect, down to the exact brain chemistry. Other times, they are twisted reflections of the person, mentally unstable, or devoid of any emotional personality.
When a Fetch dies, it will eventually change back into the refuse it was made from. Sometimes this is immediate; other times it takes years after being buried. Either way, should a fetch die before the changeling has a chance to remove it and reclaim their place with their loved ones, there's little chance of returning home, thus keeping with the title of "the Lost."
Depending on the fetch in question, a changeling must make an important choice. One option is to leave the fetch alone, seeing that there's little chance of returning to their old life. But in some cases, a changeling will try to outright kill or torment their fetch, seeing it as getting even with their Keeper for torturing them in Arcadia.
Another, albeit uncommon, choice is to befriend the fetch and somehow reconnect with it, since part of the Changeling's soul is within the fetch. This is a difficult path to choose, especially if the fetch is purely evil in mindset, and may betray the changeling to the True Fae when given the chance. Nevertheless, if a changeling does succeed in merging with the fetch, they gain all the fetch's memories, and are able to return to their mortal life without anyone the wiser.
Echoes are the powers manifested by a fetch. As magical creatures they are, fetches are hardly defenseless if cornered by changelings. Upon seeing their opposite, the fetch acquires the power of Echoes, which allow them to make it all the more difficult for the changeling to prove himself the original, sometimes even to other changelings. Worse, some echoes allow the fetch to become immune to the effects of contracts, or immediately summon the True Fae from wherever they are in the Hedge.
Rumors abound about fetches being able to mate and give birth to children. Though rare, these half-breeds are far more deadly than the average fetch, and even to mortals appears unnerving and dangerous. Some say a single fetchspawn can kill an entire freehold if not given immediate attention.
During the time of the Web of Seven, in Hellenistic antiquity, fetches were capable of becoming mortal, just as the Created do. Whether there is a means by which the Divine Principle may again mistake a fetch for one of its own remains unknown.