I think I have found out how to do that. You should climb the pillars to reach the top of tower, and from there, you would find a way leads to the inner.
Viewing post in Pseudoregalia [Jam Ver.] comments
Perchance, you are not taking about the door at the bottom that lets you into the tower, are you? I meant the door at the top! That wants four gold keys! I already climbed to the top. There's no more inner part of the tower for me to explore.
Sorry if this has just been a funny miscommunication. Alla jbierek.
I believe I know what you mean but also I don't know if we're supposed to keep these comments spoiler free?
But yes, I've done both of those. Even went back and double checked to see if I missed anything.
Either I've hit a glitch or I really have just missed something obvious. Either way, I'll be more likely to catch it on my next playthrough. And I enjoyed this game enough that I'm certain I will want to replay it.