D&D 5E Fog Cloud / Heavy Obscurement Questions

A situation arose in my group's session of HotDQ last week and I was curious if I could get some guidance/wisdom from the resident rule attorneys and other fine denizens of ENWorld.

Setup:
It's a combat scenario, party comes up against a wizard who casts Fog Cloud. As a first-level spell. There are guard drakes inside of the AOE, the wizard is outside of the AOE. See the picture below for the "GM View" of the situation.



First Question

Obviously the guard drakes within the cloud are hidden from the party's view, as is everything else in the cloud due to heavy obscurement. What about the wizard casting the spell? (Red token to the left of the AOE).

In other words, would you rule that the fog cloud's AOE blocks line of sight, making the player view this:



Or would you rule that the fog cloud AOE only blocks line of sight within the cloud, making the player view this:



It seems to me that it would block line of sight completely, granting total cover to the wizard as well. However, I'm not sure if there are official rules for this or not. But the biggest question I have is: how do you handle, in either case, a character trying to enter the square of an enemy that he can't see?

For example, suppose Vannqkorr the hasted, blessed, raging GWM barbarian, doesn't want to lose his rage by not attacking this round, so he charges the fog cloud and tries to enter the space of one of the guard drakes, what happens? I wasn't sure, so I houseruled that it burned 10 feet of movement and he was unable to enter the space (5 ft to attempt to move in, 5 ft to move back/recover balance) and had both him and the guard drake do a low DC acrobatics check to avoid falling prone from colliding into each other. Was that fair?

Are there rules for this? If so, what are they? If not, how would you/do you handle this scenario? Obviously I think it makes sense that, after attempting to move, the character becomes aware of a creature in the adjacent square and can choose to attack with disadvantage, but how do you handle unwittingly attempting to move into a square occupied by an enemy? I didn't have a problem making it burn movement, because well, the dude was a hasted unarmored barbarian so he has like a zillion feet of movement anyhow.

Also, my opinion of Fog Cloud went up a lot after this particular encounter, given that the party didn't have any wind-based spells prepared to counter it. Seems to unlock a lot of tactical options for an outgunned low-level wizard if he has a few meatshields/pets to stand in the cloud.

Fog cloud definitely blocks line of sight for those outside the fog cloud as well as inside. It's just like any mundane visual obstruction. So two people standing on opposite sides of the fog cloud would not be able to see each other.

As for running into unseen characters in combat. Is the guard drake hiding in the fog cloud? In other words, has it rolled a successful stealth check and deliberately avoided actions that would reveal its position? (Fast movement, attacking, drawing weapons, talking, etc.) If the guard drake is not super well hidden, I would rule that the barbarian detects it before actually attempting to enter the creature's square. (I would probably give advantage to a passive perception score against a creature who is standing right next to you, but disadvantage to the barbarian who is charging in, so they would cancel out.) In that case, there would be no penalty. You would just stop the barbarian and say, "Wait! There's something in the fog here with you!" Then allow the barbarian to choose what to do next.

The drake will certainly hear the barbarian if he is charging in, and if he is actively hiding, he will be able to take advantage of this. As a reaction, the drake could try to trip the barbarian. Or allow the barbarian to pass through his square but then take an attack of opportunity. Or football block the barbarian, in which case there should be a contested athletics check, probably with advantage to the drake, since the barbarian isn't prepared. Once the drake has resolved its reaction, the barbarian could continue its turn normally, and attack the drake. (Depending on what happens, he might need to stand from being prone first, but if he's hasted and has another 30 feet to burn, that's probably fine.)

On the off chance that your barbarian and drake are both deaf, they bowl into each other. The drake is knocked prone. The barbarian makes a strength save or is also knocked prone. (Advantage, in this case, going to the creature with momentum.)

Heavily obscured areas "block vision entirely". I take that to include breaking line of sight. The Fog Cloud is pretty much opaque.

The drakes inside the cloud are blinded, and can't be seen. This is not the same as "hidden". Unless the drakes actively try to hide the PCs should know exactly what square they're in. Attacks against the drakes have disadvantage because they can't be seen, but they also have advantage because the drakes are blinded, so this cancels. The drakes, in turn, have disadvantage on their attacks (they are blinded) but advantage against the PCs that can't see them, so again, this cancels.

Unless the drakes are actively hiding, then there's no problem with collisions - everybody still knows roughly where everybody else is. I don't think attempting to move into a hidden creature's space is covered in the rules - I think for a fog cloud I'd just have the mover stop short, maybe spend an extra 5' for the attempted move, and now the hidden creature is revealed.

bganon said:

Unless the drakes actively try to hide the PCs should know exactly what square they're in.

Click to expand...

Okay, got it. This is good to know. Suddenly Rezmir's legendary action to take the hide action makes a lot more sense.

bganon said:

... Attacks against the drakes have disadvantage because they can't be seen, but they also have advantage because the drakes are blinded, so this cancels. The drakes, in turn, have disadvantage on their attacks (they are blinded) but advantage against the PCs that can't see them, so again, this cancels.

Click to expand...

D'oh. This never occurred to me (both parties having adv/dadv and it canceling it out when both are in a heavily obscured area).

First of all: In this scenario, you're not going to get much in the way of definitive answers from the rules. Expect to do some house ruling.

As far as the fog cloud blocking vision beyond it, it would never have occurred to me to even ask the question. Of course it does. The idea that you can't see what's inside the cloud, but you have some kind of X-ray vision that lets you project your vision past the cloud, is absurd. Whether this is specifically stated in the rules is irrelevant. I don't normally regard "common sense" as a convincing argument in D&D (it usually means "my own irrational prejudices based on how my first DM in middle school did things"), but in this case... yeah, this is just common sense.

Now, the question of what happens when you unwittingly try to enter an enemy square is more interesting. I would be inclined to say that the barbarian must make a DC 10 Dex save or fall prone. If the barbarian makes the save, he now has a choice: He can either fall back to his previous square (thus wasting the 5 feet of movement he used trying to enter the enemy square), or he can attempt to shove the enemy and keep going (costing him an attack, per the "shoving a creature" rules). Either way, he now knows that square is occupied.

I would say that if you can't see what's in the cloud it makes sense that you can't see through the cloud. I would add though that a player may attempt to shoot through the cloud at a specified target, but must beat a hard intelligence check to remember exactly where the target was last turn and thus effectively be firing to that location without knowledge of if the target is still actually there (if he is, standard to-hit rules apply). And the player may be rewarded for their success with a scream of pain if they hit! Or mocking laughter if they miss. If there are enemies directly between the target and you, you have a % chance /# of enemies to hit one of them instead.