Your party has snuck into an enemy camp.
As the sun rises in the east at mid-morning, it appears that the targets — an adversary adventuring group — are getting ready for their move. This is your last chance at getting ahead of them.
Your party jumps into action and ambushes them with swords drawn, spells in hand. They are unaware of your presence and manage to surprise you with some punches in a surprise round.
The entire battle is enveloped by a fog sphere with a radius of 20 feet.
Fog Cloud has been cast by the enemy sorcerer.
Official RAW for Fog Cloud, the 1st level spell is: “You create an 20-foot-radius fog sphere centered at a point within your range. It spreads out around corners and is obscured. It remains for the duration of wind speed, or until it is dispersed by a wind at moderate or higher speed (at least 10 mph).
Heavily obscured are the key words. This does not mean you can’t see anything beyond what’s in front of your eyes. When trying to see in an area, a creature is effectively suffering from the Blind condition (see Condition).
Everyone in the sphere of fog is blinded unless they have Blindsight (such a bats, oozes and true dragons). Darkvision does not help here.
We now come to the blinded condition. This can be found at page 290/Appendix B of the PH.
- Blinded creatures can’t see so they automatically fail any ability test that requires sight.
- Attack Rolls against a creature have an advantage, while Attack Rolls against that creature have a disadvantage.
“Okay, I’ll try to hit him with my sword.” He was right in front me, and he was blinded as well, right?”
Our Fighter friend is blinded by Fog cloud, so she is disadvantaged in attacks. Her target is alsoblinded so she has an advantage in the attack against this blinded enemy.
Both of these forces eventually cancel one another, which results in the Fighter (and anyone else attacking anyone in the Fog Cloud), rolling straight.
“But what about my summoned Direwolves?” the Druid may ask. They already have an advantage from Pack Tactics. Shouldn’t this mean I have two advantages and one disadvantage? If so, I would be able to claim normal advantage.
Well…. no. Not if you are following RAW or RAI.
Jeremy Crawford, principal rule designer for Dungeons and Dragons stated in a March 24, 2018, tweet that “advantages and disavantages cancel each others regardless of how many things give them to you.” Either you have advantage/disadvantage or you don’t. They don’t all stack up.
Advantage and disadvantage cancel each other regardless of the number of things that give either of them to you. Either you have advantage/disadvantage or you don’t. Instances of them don’t stack up. #DnD https://t.co/ZzYzEf4Lqe
— Jeremy Crawford (@JeremyECrawford) March 24, 2018
This means that even if your enemy is blind, prone, or entangled, even if they have a help action from an allie, it cancels any the reasons you would have advantage.
So, what’s the point of casting Fog Cloud if the advantages and disadvantages it offers cancel each other?
Fog Cloud is essentially an equalizer, as it cancels out the advantages and disadvantages of each side.
If either side has an advantage (from Pack Tactics or a clutch entangle or Fairie fire, or any number of AOE spells), it is in their best interest to cast Fog Cloud or Darkness so that everyone affected to roll straight. While this doesn’t affect the fight side that was already rolling straightly, it does nullify any advantage the enemy may have had.
Fog Cloud and spells similar to it can be considered a Great Equalizer.
…And a good way for a spellcaster stop that Barbarian from pounding their head in with all those Reckless strikes.