Found 11 treasure chests in the darkness of the Tombs
This is an area in the "Death, Baby" stage where you are following Death and you must stay in her light to avoid being attacked by the darkness. There are 11 treasure chests in this area, and despite the darkness, they have a bright red border around them and are very easy to see. Just stay near the front of her range so you can get the chests and get back in her range quickly before you start to take damage. An achievement counter will pop up after each one. If you mess up, there is a check point a little before this section you can reload from.