A short theory and a thought that popped briefly into my head! From the very beginning we've received hints of the dlc. The first most prominent one being a horse overlooking a burning building. The second being a still in the cinema film of a child standing at the doorframe of a building engulfed again in flames.
This is where I take a very long shot!
Mustard gas in WW1 was known to be combustible. It was capable of creating toxic fumes if ignited, causing the need for a gas mask in the situation of a fire caused by it.
What do we see in abundance in the key art? Gas masks! What's something both of our protags lack? Gas masks! What do we know about the main 5 orphans? They all died at one point, putting them into a state of purgatory on the island.
Connect the dots!
I may be onto something but I may also just be on something.
