[RPG] Interaction between fog cloud and new vision errata rule


I am trying to understand from a RAW point of view as to how the interaction between the spell Fog Cloud interacts with the errata'd rules of vision and lighting.

First, we have the normal vision rules for 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 (see appendix PH-A) when trying to see something in that area.

Next, we have the errata:

Vision and Light (p. 183).
A heavily obscured area doesn’t blind you, but you are effectively blinded when you try to see something obscured by it.

As we know, Fog Cloud creates an area of heavily obscuring fog around the effect zone. According to the errata, it would seem as if being inside the fog does not blind you, hence, you can attack creatures outside of the fog with advantage as per the unseen attacker rules.

Am I understanding this correctly?
An I missing something?

Please advise, and thanks in advance.

Best Answer

The fog cloud spell says (emphasis mine):

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. [...]

Unlike nonmagical darkness, other heavily obscured areas created by spells such as fog cloud do generally prevent creatures from being able to see through them (unless there is some feature, spell, magic item, etc. that allows them to do otherwise - such as the warlock's Devil's Sight eldritch invocation when it comes to the darkness spell).

The distinction is that nonmagical darkness doesn't involve stuff blocking your vision, just the absence of light in that area. If there's a light shining down at point A and another at point B, and there's a bit of mundane darkness in between (but nothing else obstructing your view), then nothing prevents you from seeing the light at point B if you're standing at point A. In contrast, if there's a bunch of fog (whether mundane or magical) between A and B, it may be harder (or even impossible) for you to see B from A.

(Note that this relies on a common-sense interpretation of nonmagical darkness - the rules don't draw such a distinction, presumably because they expect people to apply logic and common sense in understanding how regular darkness works.)

As such, a creature in the middle of the fog cloud would be unable to see a creature outside the cloud, just as the creature outside would be unable to see the creature within the cloud. If one attacked the other, the attacker's advantage from being unseen would be canceled out by their disadvantage from being unable to see their target.