I don't think Ninja Castle will ever happen. Not exactly any memorable content from there...
The Dark Forest / North Woods; puzzles of speed, stealth, and patience; the Red Katana of Izlude / Level 2 Sword; the Barrel Ride; at one point, Ninji Nation; etc. It's not a huge add like Babord would be, and the server could use an actual puzzle quest.
Edit: Heck, you could have the Barrel Ride mirror the Pirate quest and have it be a daily means of collecting gralats, only the Barrel Ride offers no guarantees with how many you'd collect.