How is miss chance calculated if a caster has Entropic shield active and is inside Darkness spell?

Question

My question is simple. I have a warlock that has following invocations:

Darkness:

"This spell causes an object to radiate shadowy illumination out to a 20-foot radius. All creatures in the area gain concealment (20% miss chance). Even creatures that can normally see in such conditions (such as with darkvision or low-light vision) have the miss chance in an area shrouded in magical darkness."

Entropic warding:

"A magical field appears around you, glowing with a chaotic blast of multicolored hues. This field deflects incoming arrows, rays, and other ranged attacks. Each ranged attack directed at you for which the attacker must make an attack roll has a 20% miss chance (similar to the effects of concealment). Other attacks that simply work at a distance are not affected."

Devil's Sight:

You gain the visual acuity of a devil for 24 hours. You can see normally in darkness and magical darkness out to 30 feet.

With entropic warding I get 20% miss chance on ranged attacks as deflection. In addtion, Darkness grants 20% miss chance if the caster is in it. If I am inside darkness and I have entropic warding on, do my miss chances stacks up to 40% (given I get ranged attack) or do I roll miss chance twice as twice with 20% with each roll.

Answer 1

There are multiple ways to adjudicate this question. Technically any effects that produce a miss chance affect only by the highest miss chance in play at the moment of the attack so for a textbook answer there you go. This is to streamline die rolls during combat so that a single attack doesn't bog down the flow of the action but this restricts game play options and opportunities. So since the GM is the ultimate definer of how things work in the world they are running there are other options.

Option 1: Since Darkness creates the absence of light and Entropic Field creates light one could feasibly cancel the other or both be cancelled out because they are incompatible. This would be particularly devious result for an evil GM to deploy on a player who's trying to make their character better than everyone else in the group and thus ruining the group dynamic.

Option 2: As indicated earlier roll both separately using the Entropic Field roll only in the event that the miss chance of the Darkness is overcome. However this involves additional die rolls and may bog down combat. In any event I would not add the two miss chances together as they are not a combined effect but rather two effects happening separately in an overlapping area.

Option 3: Darkness has a larger area effect than Entropic Field thus the GM could rule that the Darkness miss chance affects anyone outside of the Darkness field. While the Entropic Field miss chance affects anyone inside the Darkness field. Since the Entropic field creates light that doesn't explicitly state it cancels the Darkness effect the two can coexist and characters within the radius of the Darkness can therefore see the swirling lights of the Entropic field. In plain game terms this means the caster only benefits from one of the miss chance effects at a time but to low level NPC's or low intelligence monsters it can look really impressive and the GM could then rule that such creatures or characters could be dazed for a round by the visual effect. This option has the benefit of sticking to the spirit of the rules and giving a bonus to the player for an interesting idea that has a limited implementation.

These are just a few options that I can think of off the top of my head. In the end the decision is up to the GM as the primary adjudicator of the game and how it effects the encounter and party balance. However if the GM decides to rule differently than the indicated rules in the books future uses should be consistent and thus be made into a House Rule and therefore something the Character can reliable expect to occur when taking similar actions in the future.

Answer 2

Use the highest relevant miss chance from concealment

The Player's Handbook on Concealment Miss Chance says, "Multiple concealment conditions (such as a defender in a fog and under the effect of a blur spell) do not stack" (152). Like most things that overlap instead of stack, only the highest amount—if any—applies, and if none of the amounts are highest only use one amount. To be clear, don't roll for each miss chance, and don't sum miss chance percentages then roll.

For example, the spell darkness offers a miss chance due to concealment, and the spell entropic shield offers a miss chance "similar to the effects of concealment" therefore the miss chance even when both should be a factor remains but 20%.

A creature that's the subject of the invocation devil's sight (Complete Arcane 133) ignores the miss chance from the darkness spell but not the miss chance from the entropic shield spell. That creature's miss chance against a foe that's warded by the entropic shield spell but that's standing in an area of the darkness spell is also 20%.

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Note: For reference, the multiple miss chances generally is addressed here, and specific rules for utter darkness (and, by extension, blindness) is here.