I don't have time to play a lot of custom quests, but I wanted to get a taste for what quest authors are doing with 2.50 features, and chose this one. I apologize for the formatting of this review: I keep trying to put in newlines but the forum software keeps stripping them out.
This review will have spoilers, by the way. Read at your own risk.
Let's start with the overall feel of the gameplay. Eiyuu is much more the "thinking man's" quest than a lot of what I've seen in the database: there are very few truly difficult fights or dungeons, and many many puzzles, and much of the enjoyment I got out of playing Eiyuu was in probing its mysteries in the overworld, and staring at a dungeon screen thinking, "how the *hell* am I supposed to toggle that switch *four* times?" The quest reminds of La Mulana or Antichamber in terms of its overall style, and this is a great change of pace from most of what I've played before. A lot of the puzzles here felt fresh and innovative, and the heavy use of custom items really helps in that regard. The green wand (I forget the name) is particularly noteworthy and I thought its potential was well-explored, as it stayed relevant across multiple different types of puzzles in different dungeons of the game. I particularly liked how it added a new (and fiendish) twist on pushblock puzzles, despite these puzzles having been around since the NES days and overused in custom quests for years.
The difficulty of the puzzles felt about right. I think the middle dungeons in particular were very well balanced: I greatly enjoyed both Sanskrit Temple and the Slidge. Brace Dest is more of a mixed bag: the top floor is solid, but the bottom floors (that you explore in the beginning of the quest) could use more polish; at the moment the dungeons lacks coherence and feels like a hodge-podge of mild puzzles and classic LttP-style gameplay, as opposed to the focused themes of the later dungeons.
Soltis is (dare I say it?) too easy. I was expecting the "hint coin" puzzle to involve setting up infinite magic loops, racing around the room in my boots to push mirrors before the magic arrives, etc. but it turned out to be very straightforward. The toggle block puzzles felt more mean than difficult here (as opposed to in Sanskrit Temple, where they were used to great effect). The order of the color puzzles on the top feels wrong: the color path puzzle should have come first, since it introduces the theme of colors equivalent to directions in a straightforward way, before the Lost Woods color puzzle adds several elaborations on the theme.
The final four-room dungeon is excellent; it's a pity it's so short. I think the third room is also broken, since it is much easier than I think the author intended. The second room is brilliant, and probably my favorite room in the entire game.
Instead of a linear sequence of dungeons, Eiyuu involves a lot of backtracking to earlier dungeons, which I think is a great feature and adds depth to the gameplay. Every room is a mystery: am I supposed to be able to beat this room yet? Am I supposed to come back later in the dungeon? Later in the game?
And of course, there are big secrets in early dungeons that you can only get to after you have very late-game items. I think this is a fine idea, but the execution was a bit weak: instead of just 2-3 places where you can come back and pick up new items, I wish there had been far more rooms, in far more dungeons, where you can profit from coming back later with new knowledge and equipment. (For example I very much expected to find color puzzles all over the place after beating Soltis, but this doesn't seem to be the case; the one place with obvious colors, the basement of the museum, is a red herring as far as I can tell.)
The story is well above-average for a custom quest, and though some of the major plot points didn't surprise me ("curse your sudden but inevitable betrayal!") there was enough meat on the story to keep me interested in exploring the world and learning more from the NPCs. I think there is plenty of room for improvement, though: first, for all of the awe that the Mask of Truth inspires, it was never clear to me what it actually *does.* It would help if there were gameplay applications to the mask (act as a lens of truth, perhaps?) that conveyed through gameplay its important to the game world. The later items also felt bland and disconnected from the story (Champion's Medal? True Champion's Medal? Why do I want these, other than just because They're There?) and the many inside jokes/references distracted from the play experience rather than adding anything, in my opinion.
And finally, my major complaint about the quest: it commits the cardinal sin of ZC custom quests, "guess the combo." One of the critical aspects of a well-designed puzzler is internal consistency, and Eiyuu *almost* pulls this off: almost every room where the wand does something has a star, and almost every room with the sacrifice blood scroll has a blood drop, etc... but sadly that's "almost," not every. There is no satisfaction to hiding a secret behind an unexpected combo. Either you run into it accidentally (oh, I randomly used the Blood Scroll and found a shop... weird) or you never find it, and neither of those give the player the satisfaction of the "a-ha" moment where they solve a puzzle and unlock a secret legitimately. Other examples that I consider unfair and unfun: the barrel that randomly reacts to your medal, and the soul game house that randomly turns into a dungeon (I still have no idea why it happened: I wandered onto the screen one time, and there it was.) There also should have been some environmental clue in the areas where you can walk through walls (Soltis does this quite well, despite being the one place where I had to ask the forums for help).
Having an NPC in a dungeon somewhere give a cryptic hint does not excuse this cardinal sin, by the way. Internal consistency is king.
 

Overall, this quest is excellent, and deserving of its place on the front page of Greatest Hits. Although I've picked apart the flaws in my review, this is to help the quest author grow with honest feedback, rather than to discourage you from playing the game. If you like difficult puzzles, a unique atmosphere, decent story, and many new and interesting scripted items, this quest has my highest possible recommendation. I don't think there is any quest in the database that packs as much entertainment in as few map screens.

I played this quest through about, like, 5 times? It never gets old for me. Amazing Puzzles, Amazing Overworld, Amazing Dungeons, Everything is amazing.
Only thing I don't like about this quest, is the length of the dungeons. They are a bit too short, but the quality of them by far make up for it.
To sum it up in 1 word: Outstanding.

This quest isn't bad, but was annoying.

This is the most unique quest i've played so far and it was pretty refreshing. The overworld has a pretty solid design with a bunch of hidden secrets, the dungeons were very enjoyable to go through, the karma system, while not as deep as some other games that have it, adds replay value which i love in video games, the story and characters were pretty solid and the music selection was pretty good.

Can't honestly find anything that annoyed me to the point of frustration and it was a very enjoyable experience. Definitely looking forward to the sequel.

I finally got around to beating this thing, I have to say this has so many cool, new, and unique items. All of the dungeons are amazing with some very cool puzzles. I really like how almost every room in the dungeons a meaning. These dungeons, despite there size, they are very complex, which I like a lot. My favorite level was ether Sanskirt Basement or Truth. Overall my only problem with this is the difficulty. This is the only reason I don't beat it till now. The reason I was able to beat this is because I gave myself the gold ring at the start of the game with a glitch I discovered that works with every quest.

Having a lot of trouble progressing, cryptic stuff should be optional, so you're not always wondering how to simply proceed

The guy running the snake house game should really heal your health via string control code when he says try again next time

Two dungeons down, feeling very trolled at the moment. Half good fun, half frustration is my experience thus far.

Hey there, great game.

I like the karma system, but it is slightly annoying, that you can miss some content. Also, is there a reason, that the eyes turn red, if I heal myself with the fairy well? Furthermore, if you choose to use the flippers to get into sanskrit temple, you have to restart, cause you have used your only key...

I fear I play in 1.5.1, is that an earnest problem? I am actually stuck in Dust Temple, most likely the Mask will be next. There is a door for my key I cannot reach and there is a screen with a talkplate and an inactive device.

BTW, I am no questmaker (no talent for it at all...) but I looked through this site enough to know who moosh is, but in a quest with this much importance to hints, aren't his footprints a danger to be misunderstood as a important hint?

Just a bit curious, but how is the quest's name supposed to be pronounced?