Interesting game ! I've see it streamed during the Aurélien's live, so I've figured out what to do and that some doors are "trap" making you loosing keys. By being attentive and exploring the maximum before open each door, I've manage to have 2 Monarch Key in my second run ! I've only travel throught 4 environments, and by looking on your map after, I see that there is a lot more, so good job for this. The mapping was coherent, but really lacks of diversity, it's the same style in a different theme. I suggest you to play more with heights ! Don't stay with 2-tiles tall wall everywhere, make differents reliefs, uses stairs, etc. Also try to play with screen tones, and work on your areas transitions. Also, even if it's a labyrinth, it's so big that somes uniques bigs things in map would be cool, like visual beacon for figure out where you are. Like a tall mountain, a great cavern entry (even if you can't go here because of stones), somes trees, waterfalls, that kind of thing.
Anyway, the map is very big, and it's a jam, but I think it's still good advices. For the gameplay it was a bit frustrating to get stucked just because you use your key on a bad door. Overall I had a good experience and I had fun, well done ! (the timer also had a lot to the rythm of the game ! Take a feature, add a timer, and that's niiice :> ). Also, good choice to go on MV to get differents styles of areas with the "dungeon tileset" rule of the jam !