Spud (#38): hint about the merciful door: the book at the beginning tells you that "He will judge the living **and the dead**". 

But all the same, now that I've unravelled most of the map (all kills, 9/10 secrets) and seen quite a few options for shortcuts, it seems like speedrunners could have a blast with this map. I haven't tried it, but it doesn't seem hard to bypass the gold key as well as the whole area containing the "merciful door", and go directly for the silver key.