If a creature is hit by multiple of the same continuous damage spell, would they all stack?
Take for instance Acid Arrow, which does 2d4 for (CL/3, max 6) rounds. If someone was hit by two of these spells with a long enough duration, both would take effect, correct?
The same should be true for Constricting Coils since each of them would force the affected person to make the save and then be free of the spell, or take the damage, right?
Best Answer
While the Acid Arrow spell has a duration of several rounds, its effect is damage, which is instantaneous.
DM_Blake, on the Paizo forums, explains it well:
While DM_Blake is not a Paizo employee, he is Executive Founder of Goblinworks, developer of the forthcoming Pathfinder Online. Given these credentials, I am reasonably confident that he has a good understanding of the rules.
(All respondents on that post, and another on ENWorld, were in agreement that that's how it works. There was no official Paizo response either way.)