Can you negate the Frightened condition by not looking at the source of your fear?

Question

As the title says, if you cause a creature to be Frightened of you, as in the Frightened condition, but they can somehow manage to not see you, do they stop rolling with disadvantage to attacks/ability checks?

Below are scenarios to illustrate my question.

Scenarios:

• If a creature is frightened of you, and they turn their back against you to hit someone else, would they no longer have disadvantage to attack rolls/ability checks?

• If a creature is frightened of you and they have Blindsight, can they close their eyes to stop seeing you, and hence stop rolling with disadvantage?

• If a creature has 60 ft of movement and is frightened of you, and there is a corner they can reach in 15 ft that will block you from sight, can they run to that corner to stop being frightened, then run back to attack without disadvantage? Assume they would not provoke OA to do this, although the OA is immaterial to the question.

Answer 1

If the source of the Frightened condition isn't within line of sight, you're still Frightened, but you don't suffer some of the effects of being Frightened.

• 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.

There's nothing here that indicates that breaking line of sight ends the Frightened condition. Specific features that inflict the condition might have clauses to that effect, but in general it's not the case.

To answer your specific examples:

If a creature is frightened of you, and they turn their back against you to hit someone else, would they no longer have disadvantage to attack rolls/ability checks?

No, they would still have disadvantage. Even if they turn their back, you would still be within line of sight, since 5e has no facing rules.

If a creature is frightened of you and they have Blindsight, can they close their eyes to stop seeing you, and hence stop rolling with disadvantage?

No. As above, line of sight doesn't require them to actually look at you.

If a creature has 60 ft of movement and is frightened of you, and there is a corner they can reach in 15 ft that will block you from sight, can they run to that corner to stop being frightened, then run back to attack without disadvantage?

They can run to a corner to block line of sight, and stop getting disadvantage on their rolls, but they are still Frightened, and they can't move back, since the second clause of the condition prevents moving closer to the source of their fear. Note that even if they could move back, as soon as the source of their fear was within line of sight, they would be getting disadvantage again.

Answer 2

Frightened imposes disadvantage on attacks and ability checks

while the source of its fear is within line of sight.

So for the first two bullets: no, unless you were using optional Facing rules (DMG p. 252). Even with Facing though, for the second bullet still no, unless you rule/houserule that the optional Facing rules extend to “no facing at all” when closing your eyes.

For the last bullet, Frightened explicitly says yes to the first part, allowing you to run away to break line of sight:

while the source of its fear is within line of sight.

and then no to the second part since choosing to move towards it is impossible:

The creature can’t willingly move closer to the source of its fear.

Before you object that you can willingly move closer once you've broken line of sight, no you can't: if you break line of sight you're not suffering disadvantage anymore, but you're still Frightened.

Answer 3

Yes. Not seeing the source of your fear means you don't roll attack and ability checks at disadvantage

The frightened condition has one effect that depends on line of sight:

A frightened creature has disadvantage on Ability Checks and Attack rolls while the source of its fear is within line of sight.

The official Sage Advice Compendium pdf offers some guidance on the meaning of "line of sight":

Question: The frightened condition says “while the source of its fear is within line of sight.” Does that mean you have disadvantage on attack rolls and ability checks even if the source is invisible but you have a clear line to its space?

Answer: 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.

The Sage Advise Compendium is clear: if you can't see the source of your fear, it is not in your line of sight, and you do not roll at disadvantage.

Let's look back at the three scenarios you offer:

Scenario 1: If a creature is frightened of you, and they turn their back against you to hit someone else, would they no longer have disadvantage to attack rolls/ability checks?

Assuming you play with the optional facing rules, a creature "can't see into its rear arc", and would therefore not have a line of sight to the source of its fear if it is behind it.

Scenario 2: If a creature is frightened of you and they have Blindsight, can they close their eyes to stop seeing you, and hence stop rolling with disadvantage?

Yes, unless the source of their fear is within the Blindsight radius.

Scenario 3: If a creature has 60 ft of movement and is frightened of you, and there is a corner they can reach in 15 ft that will block you from sight, can they run to that corner to stop being frightened, then run back to attack without disadvantage? Assume they would not provoke OA to do this, although the OA is immaterial to the question.

A frightened creature "can’t willingly move closer to the source of its fear", so they would not be able to run back.

Even if it somehow could run back, they would roll with disadvantage as soon as the source of their fear reenters their line of sight.