The World Bud, known as Bud in first installment. It is only encountered on B18F. It's found as a FOE in this room, usually warping, avoiding the player. Because of this, ambushing is quite recommended, as well as exploring the whole floor. There's an easy technique to catch this FOE : all you have to do while coming from the 17'th floor is going one step north, 2 steps east, 12 steps south then 6 steps east, the fight will begin automatically.