When you’re resolving a spell or ability, you follow the instructions in the order they’re printed on the card. So first, you destroy all the enchantments on the battlefield. Then, you gain 1 life for each enchantment destroyed this way.
So let’s see what happens when Paraselene resolves. First, we destroy all the enchantments on the battlefield, including the Festival. Once we’re done with that, we count how many enchantments were destroyed and you gain 1 life for each one. Since the Festival is not on the battlefield at this point, it won’t stop the life gain, so you’ll gain the life from the enchantments that were destroyed.
Today’s Rules tip written by Nate Long