Does the Fog Cloud spell work in conjunction with the Blind Fighting fighting style the way I think it does?

Question

The description of the Fog Cloud spell says:

You create a 20-foot-radius sphere of fog centered on a point within range. The sphere spreads around corners, and its area is heavily obscured. It lasts for the duration or until a wind of moderate or greater speed (at least 10 miles per hour) disperses it.

Now, based on the "heavily obscured" part specifically, I chose the "Blind Fighting" Fighting Style:

You have blindsight with a range of 10 feet. Within that range, you can effectively see anything that isn't behind total cover, even if you're blinded or in darkness. Moreover, you can see an invisible creature within that range, unless the creature successfully hides from you.

So the idea is that if I cast Fog Cloud, that will cause the enemy to have disadvantage against me, but I won't be disadvantaged by them? Does that work?

Answer 1

That is the basic premise

You missed the definition of heavily obscured:

A heavily obscured area--such as darkness, opaque fog, or dense foliage--blocks vision entirely. A creature effectively suffers from the blinded condition when trying to see something in that area.

Looking up blinded shows:

• A blinded creature can't see and automatically fails any ability check that requires sight.
• Attack rolls against the creature have advantage, and the creature's attack rolls have disadvantage.

As the second bullet states, "the creature's attack rolls have disadvantage." So they are outta luck.

Now, normally, you'd have advantage (because the target can't see you) AND disadvantage (because you're also in the heavily obscured cloud and can't see the target)--cancelling each other out. But since your character has blind fighting, they do not rely on sight and therefore do not suffer disadvantage and can attack with advantage.

Answer 2

This works even better than you think

The fog cloud makes the area heavily obscured, which means (p 183 PHB):

A creature effectively suffers from the blinded condition when trying to see something in that area.

And the blinded condition (p 290 PHB) has this effect:

• A blinded creature can’t see and automatically fails any ability check that requires sight.
• Attack rolls against the creature have advantage, and the creature’s attack rolls have disadvantage.

So other creatures will have disadvantage to hit you if you are in the fog cloud unless they also have blindsight.

Blind Fighting gives you Blindsight (p. 183 PHB):

A creature with blindsight can perceive its surroundings without relying on sight, within a specific radius.

You can still perceive other creatures in the cloud, as you are not relying on sight. Not only will they have disadvantage to hit you, you also get advantage on attacks on them.

One member of our group employs a similar tactic with darkness. It is very effective.

Fog cloud in many respects is even better than darkness, because it only costs a first level spell, not a second level spell, and because it is more reliable: there are a number of monsters that can see in magical darkness (for example, devils with devils' sight), but they will still be blinded by fog cloud. Even truesight is blocked. Only monsters that also have blindsight do not suffer the effect.

There is however one big disadvantage for fog cloud vs darkness: its location is static -- you will not be able to have it move around with you as you move in combat, and often combat is dynamic and requires you to move. If you want to be able to do that without losing the benefits of blind fighting, you could pick darkness instead, which you can cast on an object you carry such as your weapon so it can move with you. Blind fighting will work with that, too.