Help the weary wizard complete his disastrous food review.

I have tasted thirty different enchanted cupcakes today, and to my absolute horror, ___ turned me into a different species of amphibian.

The correct answer is every one of them.

The quantifier "every" cannot be followed directly by "of". To use it with a pronoun like "them", you must add "one" to create the structure: every one of + pronoun.

"Each them" is missing the preposition "of", and "all of it" is incorrect because "cupcakes" is a plural countable noun.