In Out of the Feywild (see review in the last post), there’s an encounter with an invisible pixie. The encounter says it trails the PCs invisibly unless they seem friendly.

What then makes the pixie interact with the PCs?

It’s a problem I’ve seen many times in adventures. The designer needs to set up a situation where the PCs have something to react to. The players aren’t role-playing every minute of travel. (Eight hours of walking where nothing happens. Yay!)

In this encounter, nothing happens to trigger play. How do the players know there’s an invisible pixie? They don’t. And it’s not likely they’re doing anything when the random encounter is rolled.

Consider if the encounter also included the players finding a wounded stag. That gives the players a choice: Do they spend time tending the stag? Do they kill it and take the meat? Do they ignore it and walk by? The pixie witnesses their choice, and then interaction with the pixie can begin.

The point with an encounter is to present a situation that then requires the players to make choices. An encounter that never happens because the players don’t realise it’s there? Try to avoid designing those!