I got through it by writing down on a paper what room it said I was in, and then would add on there what room the left or right mirrors would take me to, and then which mirrors that room would take me to, etc. Had myself a little map before long, which was really helpful because the place is like a maze. There's a lot of mirrors that will take you to the same rooms, but there's only one direct pathway to go, so you could end up set back a number of rooms if you go the wrong way.

And of course, it was my luck that I didn't find the correct mirror until it was the only mirror left I hadn't tried. x_@

I finally found my way through and now I'm getting my butt handed to me in the dungeon. stupid crappy armor.