Fictionals are a race of magical beings summoned from stories encountered in the second season of the Librarians.
According to Jenkins there are two main types of Fictionals; those that can be summoned by powerful magic and those that come into being of their own accord. The second type are iconic characters whose stories are both well written and widely known.
Though rare in the modern day Jenkins's believed there was most likely a small group of Fictionals living in the modern world; their magical existence sustained by the fame and acclaim of their stories. Also, and thankfully most of them do not cause to much trouble; the Library has also struggled to keep track of them. Flynn commented he had always heard about them but had never actually met one.
Generally Fictionals do not adapt well to the world outside their stories; Jenkins explained that their minds are only as complex has what their creator wrote meaning they may not be able to understand little if anything outside their stories. Fictionals from older or well written stories tend to have a better time adapting.
Fictionals are bound by their stories, but also empowered by them.
Though sentient beings Fictionals are bound to the narrative of their stories meaning they can be trapped and defeated in the ways their stories dictate. For example Moriarty did not die when Eve stabbed him, because that was not the way his story said he would be die. Despite this Prospero found a way to partially break with the narrative of his story such has when he managed to retrieve his spell book through magic. Fictionals can become extremely powerful if real life events parallel their narrative. For example Prospero used the white king, pearl earrings, a storm, etc. to break the magical seal on the box containing his spell book. Outside of defeating them in the way their story dictates a Fictional can be destroyed if the specific book they appeared from is destroyed.
It appears that certain Fictionals have their own opinions of their creators, with Prospero loathing Shakespeare for the ending of his story and "abandoning" him when the Bard passed away.
Fictionals were apparently quite common when magic was still in the world, but when the ley lines were first sealed many of them faded away. Despite this, some did still managed to come into existence; well-written and famous stories, such as those of William Shakespeare, interacted with lingering magic managed to draw Fictionals into the real world.
When the Ley lines were re-opened after the events of the first season, the Fictional Prospero began to enact a long-gestated plan.