[RPG] What happens if you’re frightened of a hidden or invisible creature

conditionsdnd-5efearinvisibilityline-of-sight

A Frightened creature suffers the following effects:

  • A frightened creature has disadvantage on ability checks and attack rolls while the source of its fear is within line of sight.
  • The creature can't willingly move closer to the source of its fear.

An Invisible creature has the following benefits:

  • An invisible creature is impossible to see without the aid of magic or a special sense. For the purpose of hiding, the creature is heavily
    obscured. The creature's location can be detected by any noise it
    makes or any tracks it leaves.
  • Attack rolls against the creature have disadvantage, and the creature's attack rolls have advantage.

What happens if the source of a creature's fear is invisible or hidden?

More concretely:

  • A Wizard uses Cause Fear to frighten an Ogre, then puts on a Cloak of Invisibility. On the Ogre's turn, he tries smack a Fighter standing next to him. Does the Ogre have disadvantage on the attack roll?
  • On her next turn, the Wizard Hides from the Ogre. When the Ogre tries to smack the Fighter again, is anything different?

Here are two related questions that may help answer this one:

  • This question asks if the frightened creature can avert or close their eyes to avoid the disadvantage. The answers articulate the difference between line of sight and being able to see a creature. Does anything change if the source of the fear is invisible?
  • This question asks if the second bullet point of the frightened condition allows a frightened creature to "supernaturally" detect the location of the source of its fears. Would the first bullet point of the frightened condition allow a frightened creature to supernaturally detect the presence of its fears?

Best Answer

If source of fear is invisible, frightened creatures aren't affected by disadvantage.

A line of sight is the direct path between a viewer and viewable object [1,2,3]. Without an object to view, such as the cause of one's fear, there is no line of sight to that object. So when the a creature is not viewable, by hiding or invisibility, there is no line of sight to it. In short, one does not have line of sight to something they cannot see.

Being invisible is not within line of sight.

Barring magical senses, sight passes straight through invisible creatures in the same way it passes through air or a pane of clear glass. If the source of the fear is invisible, it is no longer in the targets line of sight.

This aligns with the vernacular and game mechanic definitions of invisibility.

Similarly being hidden is out of sight.

Successfully hiding makes a character unseen. Being unseen is, by definition, not within line of sight. So the cause of fear is not within the line of sight and does not incur disadvantage on attack rolls.