However, it's heavily implied that it contains:
* A Jigsaw trap: The box is very similar to the ones used in previous Saw movies to deliver traps.
* A message from Jigsaw: It's likely that the box contains instructions or a message from Jigsaw himself, just like the other boxes.
It's important to note that the exact contents of the box are never revealed in the movie. The focus is on the psychological game Jigsaw has set up for Jill and the consequences of her actions.