I was playing Hexxit today, and discovered a weird castle I've never seen before. It was generated with the castle spawner. There were skeleton spawners and a necromancer inside (though that doesn't particularly matter). It was comprised mainly of sandstone and blue wool, but bricks, end stone and stone slabs were there too, particularly on the staircases. It wasn't a kamiPalace, since it wasn't above ground; but I don't know what it is.