Cthulhu fluxx is a nice and well rounded 'hard' version of Fluxx I would say. It is VERY well balanced as far as action/rules/creepers etc cards in the deck. Not too easy but not too hard. Of the variations, I feel like it is one of the best as far as experiences as to what Fluxx can be. Also being a fan of Lovecraft, I enjoy the references. I wouldn't recommend it as a first version to play, but it is definitely one to enjoy.