Gaming Spoilers-SSE Question

[Alerek]

I'm stuck at the end here, I'm at 83%, have a bunch of flags on my levels, some with some crowns on em...but at the level towards the end that has the map and everything, I cleared all the boss fights and character matches, but I dont know where to go next. Someone on another board said I needed to go to a certain room, but I can't seem to find it. I've been everywhere I can, if I'm not mistaken. Any insight on how to progress?

Edit- I was sleepy, and drunk last night when I played most of it, and theres a really obvious door I didn't go through. I'm an idiot.