I ended up coming out of that door. I somehow obtained lv4 armor w/o collecting all of the skulls. I have 7 so far. Have found all of the magic pots. Just need to find lv4 sword then off to final layer. Nice quest but there are a lot of areas that don't run that smooth.
Also, do you need the flute/orcania to beat the final boss? I do not have it.
Edited by matski, 17 December 2014 - 10:16 AM.