D&D General Invisibility, line of sight, and the frightened condition

[Pickaxe]

I was looking at the gloom stalker ranger subclass and was wondering how Umbral Sight and the Fear spell, which gloom stalkers get at 9th level, interact.

Fear imposes the frightened condition, which affects creatures while the source of their fear is within line of sight. In darkness, a gloom stalker’s Umbral Sight makes it invisible even to creatures with darkvision. If a gloom stalker casts Fear while in the dark, do those who fail their save not suffer the affects of the frightened condition if they can’t see the gloom stalker? Similar issues arise with monsters that have fear effects but also some sort of concealment in dim light, e.g., shadow mastiff alphas.

Part of the issue is the definition of “line of sight,” which does not seem to be defined in the PHB, and the index refers you to the Targeting heading of casting a spell, which does not use the phrase “line of sight” but talks about a “clear path” in terms of cover. Is “line of sight” entirely a matter of cover, or does it include concealment, like being hidden or invisible?

Thanks!

Axe

 

[jasper]

At 9th level how much damage can a Gloom stalker pump out? If you can't see it, Gloomy has just wasted the affect.

 

[Oofta]

Line of sight means just that. Can you see the source of the fear? Yes or no.

 

[jgsugden]

The spell says:

You project a phantasmal image of a creature's worst fears. Each creature in a 30-foot cone must succeed on a Wisdom saving throw or drop whatever it is holding and become frightened for the duration.

The target does not need to see you in order to have these impacts. If it fails the save, it drops what it is holding and becomes frightened.

While frightened by this spell, a creature must take the Dash action and move away from you by the safest available route on each of its turns, unless there is nowhere to move.

This also takes place regardless of whether it can see you. At the start of their next turn, they take the dash action and move away from you by the safest route available, unless there is nowhere (safe) to go. They'll continue to do so until they are no longer frightened by this spell.

If the creature ends its turn in a location where it doesn't have line of sight to you, the creature can make a Wisdom saving throw. On a successful save, the spell ends for that creature.

This is the only place where being able to see you matters. If they see you, they get no save and the spell continues as long as you concentrate (up to 1 minute). If they can't see you, because you're invisible, behind a corner, hiding, or whatever other reason, then they get a save to try to end the spell.

 

[Pickaxe]

Line of sight means just that. Can you see the source of the fear? Yes or no.

While that sounds right, it has some implications for things like the frightened condition and creatures that impose it. If a shadow mastiff alpha uses its Terrifying Howl to cause creatures within 300 feet to have the frightened condition and uses a bonus action to become invisible with Shadow Blend, do the frightened creatures not gain disadvantage on rolls because they cannot see the mastiff, even if the mastiff has line of sight to them?

I could see how “line of sight” might be more about the cover rather than concealment, which would make sense if a howl was the source of the frightening effect.

Either way, it’s a little surprising that the phrase “line of sight” is not defined anywhere in the core rules, as far as I can tell.

 

[Bayushi_seikuro]

I would think being invisible and making something Frightened of you wouldn't work per Sage Advice.
However, the fear spell doesn't make them afraid of you, but of some image in their brain: You project a phantasmal image of a creature's worst fears. Each creature in a 30-foot cone must succeed on a Wisdom saving throw or drop whatever it is holding and become frightened for the duration.

The frightened condition says “while the source of its fear is within line of sight.” Does that mean you have dis-advantage on attack rolls and ability checks even if the source is invisible but you have a clear line to its space?
No. If you can’t see something, it’s not within your line of sight. Speaking of “line of sight,” the game uses the English meaning of the term, which has no special meaning in the rules.

 

[jgsugden]

While that sounds right, it has some implications for things like the frightened condition and creatures that impose it. If a shadow mastiff alpha uses its Terrifying Howl to cause creatures within 300 feet to have the frightened condition and uses a bonus action to become invisible with Shadow Blend, do the frightened creatures not gain disadvantage on rolls because they cannot see the mastiff, even if the mastiff has line of sight to them?
...

Terrifying Howl. The shadow mastiff howls. Any beast or humanoid within 300 feet of the mastiff and able to hear its howl must succeed on a DC 11 Wisdom saving throw or be frightened for 1 minute. A frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a target’s saving throw is successful or the effect ends for it, the target is immune to any shadow mastiff’s Terrifying Howl for the next 24 hours.

There is nothing in the Shadow Mastiff Alpha's (SMA) ability that is impacted in any way by whether you can see the SMA or not. The visibility of the monster is only important when the rules say it is, and most monsters that can turn invisible have not been built so that they need to be seen to be effective.

 

[Hriston]

The DMG (p. 251) defines line of sight as existing between two spaces when at least one line from a corner of one space to any part of another space does not "pass through or touch an object of effect that blocks vision".

 

[Umbran]

The DMG (p. 251) defines line of sight as existing between two spaces when at least one line from a corner of one space to any part of another space does not "pass through or touch an object of effect that blocks vision".

I would say invisibility blocks vision.

 

[Hriston]

I would say invisibility blocks vision.

I would agree with this.