You used the word palindrome to determine the notes you were going to play. You added more complexity and a stern limitation to an already complex and limiting challenge and for that, I commend you. It was a very creative endeavor. These aren't bad orchestrations at all, but if I could give some advice and critique, they are very simple, and very repetitive, but not because you limited yourself. If I could, I'd recommend a higher focus on keeping things simple, and if you give yourself a tonal limitation like you did, then focus on the Rythm instead. And keep the tones simple and less repetitive and aggressive. Atmosphere works best for gloomy castles.
I wish you well. 👍🏻