8759M Battle of Micro Nui

While not from a castle theme its still a castle, it has a drawbridge, a portcullis, traps, 2 catapults and is a heavily fortified building, so it acts like a castle, looks like a castle, so it must be a castle.

Jokes aside Battle of Metru Nui was a playset released during the 2005 world premiere of the short live system Bonicle line and was the flagship set of that line. While not part of a castle theme the castle inspirations and designs implemented are hard too overlook. Its a sci fi castle or at the very least a fortress. Besides Bionicle can't have too much representation tbh.