Wow. I have just really started going through the vastness of Newgrounds audio side. From the first few moments I heard Den-X I clicked fave. Thus I bestow on you my MASSIVE voting power of 5.26. Great stuff and I look forward to listening to more.

Well well ... after a few problems with censorship, I finally managed to connect myself to an external SSH tunnel and here I am! Ready to review, I didn't forget you :P

All right, time do un-mount this Lego. For this review, different themes will be treated as T1, T2 and so on, depending on the sequence and similarity.
You start with a heavy theme (T1) that lasts until 0:26. T1 is a slow an powerful theme, and definitely doesn't prepare the listener for the sweet girl voice that has place in T2 (starting at 0:27). T1 has a strong drum presence and a heavy guitar to match - kinda what a heavy metal fan would expect. Then at 0:27 (T2) change the theme radically to match the voice - and you make a really nice change imo, you make it look easy. I really like T2, and the singer is really alive. In T2 the rhythm is still fast and the guitar seems to be higher to match the voice (Nice!). Fast guitars with singers that have a nice power of expression really kick ass. Then, at 0:50 you start with T3. This theme is waaayyyyy slower than T1 and T2, and I personally don't like it that much. I guess your idea is to make the song more melodic, but there are faster ways to do it (like in T2!). IMHO, T3 kinda breaks the mood. At 1:15 you return with T1 followed by a quick pause at 1:38 and then you get back to T2. Man, you guys (and girl) really must love these two themes. Well, to be honest I can't blame you, T1 and T2 really rock the house. At 2:03 T4 enters. yet again another really slow theme following T1 and T2. I am starting to think that this is in purpose, that you want this piece of music to have both fast paces and slow melodies. This is usually good to have a large number of fans, it's "easier to hear" and having in mind you are still starting with your project I can't blame you for this choice. I do have to say however, that you kinda kill the song for some of the hard-core metal fans out there. Still, on T4 you have a nice and relaxing guitar solo, (2:27) that really adds some good quality to T4. Then at 2:51 (nice choir!) the fun begins... man oh man. One thing jumps into my mind -> Arabic feeling! (I still remember in the good old days when I wanted to mimic the feeling of Arabic music using sets of minor scales in the trumpet :P ). I never thought I would hear something similar in a metal piece... I guess you had to be the first one xD.
At 3:44 you get back to T2 again and then you make a transition to finish with the good old T1.

Review:
well, this was a nice Lego to un-mount, I was starting to miss this kind of action. In my humble opinion (imho), repeating T1 and T2 nearly 3 times each one makes the music epic, but it also gets the listener tired after a few hours of hearing to it. I understand that you try to mitigate this factor with themes T3 and T4 but those are really slow and calm, they don't fit at all with T1 (starting and ending theme). I guess your main idea was to make them fit with T2, and that was achieved with success. Then there is the arabic theme: something I have never heard in NG, truly a gulf of fresh air. T3 and T4 make this music easier to hear for masses but may disappoint some "hard-core" metal fans - there is nothing wrong with this, it's a choice and I think you're doing the right one, just please add the singer in T4 if there is a time :P

Final score:
Well, this review is over 1000 chars so I guess I better shut up now. I want to say a few things: the singer was a hell of an addition to this project, I REALLY look forward to hear more from her angelical voice in your project, and the arabic theme was really good. I have seen Portuguese bands that are not as good as this one making a name in reverbnation (metal bands) just because their singer is freakin hot and also has an angelical voice - my guess is that you guys could give it a try (however you need to consider the fact that Portugal Metal Bands are few when compared to Northen Europe or even American bands, and thus PT bands profit from a smaller market).
Score: 5
I have about 55 chars to say this: GL in future, I'll keep an eye 4u.

she sounds like the singer in Envy's Come Home :)

I started the song all like, "Yes, a singer finally!" Listened in anticipation to the first few seconds. Then she sang. I shivered with chills. Then the slow part started and she sang like a siren... and I wept. Brilliant song, my friend.

This is freaking awesome, though I already told you that =P