So, I'm near the end game and about to go after the SK. When I get there, I find the castle gone, and the SK just standing there out in the open.
I tried to attack him anyway, but there is a invisible barrier preventing me from getting near him.
As a side note, near the end game, the red line of the doomsday counter would completely disappear, even though it was more than half way through.
https://www.dropbox.com/s/jmw8gcdfqo950hk/whereisSKCastle.png?dl=0