Ancient archetype. Also, Threshold Guardian. Before being able to enter a strange world, or obstructing the treasure that is the goal, a hero is likely to encounter an opponent in the form of a Gatekeeper or guardian. The term Threshold Guardian refers specifically to the point in the Hero’s Journey between the ordinary world the hero must leave and the unknown world she must enter. In other words, the threshold between act one and act two. See Archetypes.