draco2005 said:
"The creature is immune to any poison it is exposed to during the duration of the spell...." only applies if you have been exposed to the poison earlier, and re-exposed to it again at a later time, providing the spell's duration has not expired. That is my interpretation of the spell.
While this question always sounds terrible, it's not intended that way. Is English your first language?
What you're describing would be written "During the duration of the spell, the creature is immune to any poison it
has been exposed to." Or, better, "it has been previously exposed to".
"Expose" is an immediate sort of verb.
Compare, say, "The creature is immune to damage from any weapon it is struck with during the duration of the spell." If I hit the creature with a sword for the first time during the spell, it's immune to the damage, right? Whereas if I write "During the duration of the spell, the creature is immune to damage from any weapon it has been previously struck with," the creature will only be immune to the second hit. The first time, it's not a weapon he's been struck with.
But if I had hit him with a mace last week, and he casts the spell and I hit him again, he'll be immune immediately, since at the time he cast the spell, the mace is
already a weaopn he's been struck with.
Can you see the difference between "is struck" and "has been struck"?
"expose" behaves in a similar fashion to "strike". "is exposed to" is an immediate description. "has been exposed to" refers to prior events.
Contrast, say, "The creature is immune to any poison it is familiar with." By its nature, even though we're using a present tense verb clause (it is familiar with), we're referring to prior events - the events by means of which the creature became familiar with the poison. But "expose" doesn't behave that way.
If you (mistakenly) understand 'be exposed to' to be more like 'be familiar with' that 'be struck by', your interpretation makes sense. But since it's based on a misconception, your result is wrong.
-Hyp.