Beyond The Grave

I'm currently in Death's mansion, and I decide to see if I can get into the room that he calls "Bad for both of us". I'm not sure if talking to him about my options triggered it or if it was something else, but I was able to get in. I figured out the code was "tombstone" and it gave me something along the lines of "You hear the shattering of glass somewhere at the back of the mansion" but I've looked in every room I know of and I can't find where that might be. I haven't fought the guy Death is directing me to yet, so I'm not sure if I was supposed to do that first. (I don't see why, though. When you have a puzzle right there, someone is gonna want to solve it asap) Does anyone know where to go from here?

 

Try watching a video Guide on the quest, as it will show you more clearly than any other thing I can say: