Personally i usually don't like characters who are introduced in later seasons like Uron Greyjoy or Ezri Dax from Star Trek: Deep Space 9, unless they are foreshadowed. They also intrude basically blood magic out of nowhere. Again something not foreshadowed.
Actually I don't think it was completely out of nowhere, as in the first season there was a bad rumor surrounding Moonshadow Elves and how they drank blood. Which now we know those rumors actually came from Kim'Dael and her cult. Plus also we saw Kim'Dael in the Bloodmoon Huntress comic, so if you read that then she didn't come out of nowhere. But I get what you're saying and that is valid too!
