It specifically uses the wording that the auras are cumulative.. that suggests that the damage is actually together.
True. What get's hard to adjudicate is when you have multiple overlapping auras from them.
The Chillborn Zombies are spaced such that you hit one zombies aura, then two overlapping auras, and then 3 overlapping auras if you keep moving. How is the cumulative damage calculated?
You enter the first zombies aura, but are not in the other zombies aura yet. You take 5 damage
You keep moving, you hit the 2nd zombies aura. Does it deal 10 damage because it's cumulative with the 1st aura (meaning that you have now taken 15 cold damage)? Does it deal only 5 because you have already taken 5 from the 1st aura?
And then you hit the 3rd aura which is just overlappting with the other two - 15 damage? or 5?
Do you count it as one big aura and deal the 15 damage once? Or as seperate aura's that each deal the cumulative damage if they are overlapping?
And how does it interact with cold resistance 5 in this case (it's cumulative, so does the 5 you resisted the first time not stop the additional cold damage for entering a 2nd aura?)
The last time I ran into this situation I had the aura's doing damage for each one you entered, incresed to 10 or 15 damage if it was an overlapping aura, but had cold resistance resist each instance of damage seperately. Not sure if that was correct (as it meant you effectively took damage from the same aura twice - once when entering, and again when entering the square where it overlapped with another cold aura), but the PC's were mauling the zombies anyway.