If an attack is obstructed by two gas clouds, it seems clear the defender only gets one additional defence die, but is the defender able to change one blank result to an evade result for each cloud? It seems like they might.

Rule on obstructed shots:

"An attack is obstructed if the attacker measures range through one or more obstacles. If an attack is obstructed, the defender rolls one additional defense die during the Defense Dice step."

Rule on Gas Clouds:

"When a gas cloud obstructs an attack, the defender rolls 1 additional defense die, and may change up to 1 blank result to an [evade] result."

Also, if the effect of multiple obstacles is not cumulative, what happens in the future if new obstacle types are introduced with new effects? eg, shot is obstructed both by a gas cloud (granting effect A) and obstacle X (granting effect B)?

Good question, as of now my gut says that the blank-to-evade is not cumulative. I only say that though because most of the effects in this game that use "and" place the same restrictions and requirements across both sides of the clause.

No rules to back this up, just the trend of existing interpretations.

there is no ruling for this, since there is no new rules reference for the new obstacles yet.

RR page 13:

OBSTRUCTED
An attack is obstructed if the attacker measures range through an object. If a ship or device obstructs an attack, there is no inherent effect. If an obstacle obstructs an attack, there is an additional effect.
• If at least one asteroid or debris cloud obstructs an attack, the defender rolls one additional defense die during the Roll Defense Dice step.

since this is the only thing we have to go by, i would rule that the effect is not cumulative, since the effects of multiple obstacles don't stack to begin with.

it would be much appreciated if you would pose this question to FFG from here:
https://www.fantasyflightgames.com/en/more/contact/

Something else that came up recently for me:

Which obstacle do you count as the one obstructing? If you measure through an asteroid AND a gas cloud, do you go by which one you measure through first/closest and use the rules for that?

2 minutes ago, InterceptorMad said:

Something else that came up recently for me:

Which obstacle do you count as the one obstructing? If you measure through an asteroid AND a gas cloud, do you go by which one you measure through first/closest and use the rules for that?

the gas cloud is obstructing either way, so you get the benefit from it, even if there are other obstacles besides the gas cloud.

5 hours ago, Rossetti1828 said:

It seems like they might.

They dont. You quoted the relevant rules.

"An attack is obstructed if the attacker measures range through one or more obstacles. " This says it doesn't care how many obstacles obstruct it. Its a binary yes or no condition. Is it Obstructed? Yes or No.

" When a gas cloud obstructs an attack.."

As seen above, it doesn't care how many clouds obstruct. Gas cloud will either obstruct, or it doesn't. So only 1 die result will be able to be changed, and 1 bonus defense die granted.

"Also, if the effect of multiple obstacles is not cumulative, what happens in the future if new obstacle types are introduced with new effects?"

Each obstacle has its own effect. As quoted above, (and in the rules reference) if a Gas cloud obstructs, do this, if an Asteroid obstructs, do this. So each different type would trigger its own effect, but only once, no matter how many are actually obstructing it, because it would be written like the gas cloud, asking if that type of obstacle is obstructing it.

Think of the obstacle effects as cards. Asteroids have their own effect, Debris have their own effect (just so happens that neither of them do anything on their own), Gas Clouds have their own effect, Trick Shot has its own effect, Blackout has his own effect... All triggered off of being obstructed and by specific obstructions (Trick shot and Blackout looking for obstructions by obstacles)

4 hours ago, nitrobenz said:

No rules to back this up

All the rules he quoted are backing it up

2 hours ago, InterceptorMad said:

Something else that came up recently for me:

Which obstacle do you count as the one obstructing? If you measure through an asteroid AND a gas cloud, do you go by which one you measure through first/closest and use the rules for th  at? 

All of them. If the asteroid did have an effect from obstruction, it would also be applied as well as the gas cloud's effect. So if your example happened, the asteroid wouldn't be doing anything in addition to what the gas cloud isnt already doing by itself. If (for example) they decide to make, i dono, and Ion Cloud, and its effect was if it obstructs an attack, you roll one less attack die, and your shot was going though both the Ion Cloud and the Gas cloud, the end result would be you roll one less attack die, the defender roll one more defense die, and can change a blank to an evade.

While it is entirely possible, i somehow think that if FFG decided to make new obstacles, their effect of obstruction would be something that wouldnt conflict with effects of the gas cloud as to make it confusing.

Nice breakdown @Lyianx

Well ok... But to be clearer they should have written:

"When one or more gas clouds obstruct an attack, the defender rolls 1 additional defense die, and may..."

instead of what they did write:

"When a gas cloud obstructs an attack, the defender rolls 1 additional defense die, and may..."

Yeah, I think we all know by now, FFG isnt perfect when writing their rules. Sometimes they write it in such a way that they contradict themselves. Although its possible they could come back and rule that each one counts for its own bonus, I think that is unlikely given how obstruction currently works.

4 hours ago, Rossetti1828 said:

Well ok... But to be clearer they should have written:

"When one or more gas clouds obstruct an attack, the defender rolls 1 additional defense die, and may..."

instead of what they did write:

"When a gas cloud obstructs an attack, the defender rolls 1 additional defense die, and may..."

Honestly speaking, while not perfectly-clear, current wording is not misleading.

If multiple clouds obstruct, it is true that "a gas cloud " obstructs. It is also true that multiple of gas clouds obstruct, but there is no game effect taking place out of that precedence.

39 minutes ago, Ryfterek said:

Honestly speaking, while not perfectly-clear, current wording is not misleading.

If multiple clouds obstruct, it is true that "a gas cloud " obstructs. It is also true that multiple of gas clouds obstruct, but there is no game effect taking place out of that precedence.

This is pretty much it. The current rules treat obstruction as a true/false binary and numbers are not taken into account. When FFG means for an effect to be cumulative they tend to to use words "for each". Not a hard and fast rule though.