What do you mean by 'it blocks the layers underneath'? The multiply effect seems to be working correctly... Also, just having the bottom layer as black and non-transparent was creating this extremely strange issue where the player's sprite was creating a 'trail' everywhere it went.
Anyways! I cleaned up/standardized the layers (for at least N S E W, haven't implemented the diagonal corner rooms yet b/c I want to get the basic interaction working), implemented a standard system of variables for where to spawn the player on each map... and it's still not working.
Capx: http://www.filedropper.com/zzttest_3