Fallen Knight

 

The Heart of Chaos is missing just a couple of strong heroes with good armies, which I would place on the side of the Dark Elves. Otherwise, only one decent hero with a more or less normal army appeared to me, and even she was defeated without any losses on my side; the rest of the castles were just a joke. I crushed them all, except for the last one, where Chaos magic sent all my troops back to the gods. If it were made like in the 3rd mission of the original Rai'lag campaign – where you have to capture a clan from scratch, so that each castle has a Dark Elf of level 20-25 and a lot of Chaos magic, then yes, then it would be much more challenging. Chaos itself is already a huge imbalance, and if you go for ballistas and Chaos magic, it's just insane.

Added 3 minutes later
Story-wise, the Heart of Chaos is a very cool mission. The dialogues are amazing – as far as I understand, they were all taken and reworked from the original game to make it look authentic, and I was incredibly impressed by this. I don't understand how anyone could dislike this mission. If you add more hardcore elements, it would be even better. The map itself is small and can be completed in an hour or two; how can you get bored with it, unlike the Fallen Knight, which took me a whole day to complete.