Fantasy is a genre literal and is true to her name. She has blue skin, black hair and elven characteristics. She appears to be soft spoken and calm unlike her twin brother Science Fiction. She's also the older sister to an unseen literal Superhero. She was called upon by Kevin; who was under the influence of Writer's Block. However, he still found even with the genres here, that they were boring. Bigby, Snow, Gary, and Mister Revise; along with the Page Sisters, had come to stop him from doing further damage to reality. Kevin sent the Genres, including Fantasy to guard his house and fight off the others.
It appears that Fantasy wanted to stop the fighting as she sent a unicorn to call a momentary truce. However, it might have been a ploy to trick the group. Whatever the case, Priscilla Page didn't want to hear it, she stated she had always hated Fantasy. Bigby, who had been put through much humiliation and transformed into a girl to further it, lost his patience. While Robin, Priscilla, and Hillary fought off the others, he snuck around trees and attacked all the Genres.
While the other Genres didn't take Bigby seriously in his form, despite Horror's warnings. That would be a mistake as Bigby would show no mercy and kill Fantasy and the rest of the Genres. For the moment, after defeating Kevin, Fantasy and the rest of the Genres had apparently recovered. Or it meant they were resurrected by Kevin or simply replaced. They were all sent into a new world where Kevin could do what he want and leave the mundy world alone.