Can someone with Devil's Sight see inside a Fog Cloud spell while a sphere of Darkness remains at the centre of the fog?

Question

Basically, in a session, we had the party come up against a group of Bugbears who attacked the party in an ambush. In a moment of haste, the party's warlock cast Fog Cloud to help obscure against the bugbears to try and cause an even ground for the fight. At the same time, to give their team an edge, the Warlock cast Darkness on one of their allies' blades so that they could see within the darkness and give at least two of the members who had Devil's Sight advantage in the fight.

If someone casts Fog Cloud and then another person casts Darkness within the area of fog, does the darkness basically remove any trace of the fog within, even for those with Devil's Sight? Or do those with Devil's Sight see nothing but the fog within the darkness?

I would like some clarification as to know in the future how to react to this, should the tactic be reused.

Answer 1

You would see only fog

The rules for heavily obscured areas reads as follows:

A heavily obscured area—such as darkness, opaque fog, or dense foliage—blocks vision entirely.

Devil's sight does let you see even in darkness. But that is separate from the obscuring effects from things such as heavy fog as indicated in the rules text. You can think of it like casting a darkness spell on the other side of a brick wall. Even being able to see into darkness doesn't mean you can see through the wall.