One way to control the plot of an RPG is to place barriers in the hero's path. A destination may be unreachable without access to water transport because the main character has Super Drowning Skills. You may need to become immune to fire before moving on because the next level is set in a Fire and Brimstone Hell environment. Perhaps you need to enlist the help of a specific NPC, or acquire a specific item, in order to get past the annoying guard. Examples of You Must Be This Tall to Enter include: