Here's the spell
Just want to clarify that means for each successful hit a creature lands they take 2d6 swarm dmg and must make multiple saves if they landed multiple hits ?
so if they land 3 hits they take 6d6 damage and must make 3 saves vs poison
Yep. In the case of an enemy making a full-attack and hitting you three times...
Enemy attacks successfully -> Fort save -> Poisoned for 4 rounds (I just picked a number. You use what is in the poison entry)
Enemy attacks successfully -> Fort save +2 -> Poisoned for 6 rounds (+ 1/2 normal duration)
Enemy attacks successfully -> Fort save +4 -> Poisoned for 8 rounds
Your turn -> You do stuff
Poison affects enemy -> 7 rounds left
Enemy attacks successfully -> Fort save +6 -> Poisoned for 9 rounds
Once the enemy satisfies the cure conditions, though, all instances of the poison are cured.