My final quest from the contest! let me say ahead of time that the main reason why this quest is going to end up with a relatively low score is because of it missing a lot of what makes a proper 5th quest- but more on that at the end.

I liked how each dungeon had a completely different feel to it. Lots of gimmicks to learn and develop. For the most part, you are eased into the concepts slowly enough to learn them, but quickly enough that you don't feel hand-held. I thought that "level 2?" was a very cute idea. The way I explore, I found it before actually clearing dungeon 1, so I was very curious as to why the question-mark. Of course, I didn't explore it until finishing dungeon 1, so by then it made sense. Very clever.Dungeon 4's lighting effects became annoying fairly quickly. I would suggest not having the blinking in more than 1 or two rooms. Having the darkness return, however, is perfectly fine.
Limited use of annoying concepts is really the key to what could have improved several dungeons. Case in point: dungeon 6. The reverse controls is cute, but does become more of an annoyance than anything else well before the level is finished. My suggestion, to keep with the "poison lake" theme, would be to have an "antidote" item (perhaps as a dungeon treasure in level 6) that would negate the reverse-controls. Perhaps even make it a location in the dungeon that has effects that you are told don't last long (and so when you hit the reverse area in dungeon 9, there is an explanation- the antidote's effects wore off).
Similarly, the pathfinding in level 7 was very tough. This is the only time during the contest maps that I needed to draw a map outside of my standard mapping sheets (I have a nice 1-page document with spaces for the overworld, all 9 dungeons, and note space; this sufficed for all 16 of the other contest maps, and except for dungeon 7 here, was fine for this one). Having a few paths "mis-connected" like this is fine, but you went overboard here.
Dungeon 8 had unintended problems (which recurred in dungeon 9). Due to the unpredictability of certain bosses (lanmolas, patras are the main culprits), I had several melting rooms where the boss hung out along the edge, and so I had no chance to defeat it. Forced deaths, especially after going through 5 to 8 time-sensitive rooms in a row really ruins things. I would say that since there are plenty of extra rooms on this map, checkpoints would have been nice- Put a key-door in several rooms to a blank one, and provide the key in the previous room. Use that door as a 2-way path to the entrance area. Only 1 or 2 such changes on each half would have made this a lot less frustrating.
Aside from the annoyances, however, the map was generally very easy, which is why it really doesn't fit as a 5th quest (as you, yourself, implied earlier in this thread) Also, all the twists and gimmicks really caused it to lose the feel of the earlier quests. Now, I like puzzles, and so I really enjoyed most of the quest. Unfortunately, I have to rate it based on the purpose of the contest.
Highs and lows combined, I give this map a 3.28 out of 5. If this were NOT a contest map, it would have earned almost a full point more- the problems mentioned above being the only things I can mark it down for- and as I said, much of that was overuse of the gimmicks, not flaws in the map.