Liminal is a self-contained tabletop roleplaying game about those on the boundary between the modern day United Kingdom and the Hidden World- the world of secret societies of magicians, a police division investigating Fortean crimes, fae courts, werewolf gangs, and haunted places where the walls between worlds are thin. The players portray Liminals - those who stand between the mortal and magical realms, with ties to each.

Examples of Liminals include:

- A magician who acts as a warden to protect unaware mortals from supernatural menaces; 
- Someone of mysterious birth who is perhaps half Fae. In any case they are caught up in Faerie politics whether they like it or not. 
- A burglar who steals supernatural relics. 
- A werewolf who still has many ties to ordinary people. 
- A dhampir, striving to do good despite their vampiric infection. 
- A mortal detective who knows some of the real strangeness out there.

The magical world has a basis in British and Irish folklore and legends, along with ghost stories and modern day popular takes on the supernatural in fiction. Inspirations from fiction include the "real world" fantasy novels of Ben Aaranovitch, Jim Butcher, Emma Bull, Susanna Clarke, Harry Connolly, Charles de Lint, Neil Gaiman, Benedict Jacka, and Helene Wecker.