Welcome! Always happy to give feedback. Please take what I say as constructive, honest feedback and keep in mind I'm just one person.
Main Theme - I liked the opening but by 47 seconds in, I was ready for a different, more distinct texture. I can hear the trading off, cycling and even doubling of parts between the voices and the strings but they just kind of meander around. It also doesn't help that the vocal patch is very synthy sounding and is all composed of the same vowel shape.
You can create a sense of epic scale and progression while having a more stable and set melody. Oblivion's main theme comes to mind:
After a little prelude it becomes VERY clear what the melody is and what parts of supporting. In your main theme, which should traditionally be the most iconic melody of the soundtrack, it's hard for me to really know what your melody is from just one listen. You have some really nice moments and overall the production is pretty good! I just think you need a bit more focus on your melodies. Perhaps even the arrangement - i.e. how the rest of your track supports and interacts with that melody.
Also check out Spitfire Labs Choir - it's free. And it sounds GORGEOUS. The attack is VERY slow so this free patch will only work on certain styles of writing. But it will sound so much more realistic than the vocal patch you're currently using.
Quick point on Lands of Shadow - your drums are distracting here. It's not enhancing but rather subtracting from the experience. I would work on the mix between your percussion and your other instruments. And be careful of things that repeat for too long and are higher pitch (i.e. 3:04). That can get REALLY annoying, really fast. Try and look for ways to create tension and progression without being so repetitive. Try things like changing to other instrument sections, changing textures, etc. This track, in my opinion, is way too repetitive to be effective, honestly.
With ambient music you can afford to really pare things back. Less can become way more in this regard.
Even the more tense areas can be served with less activity to truly keep the music more ambient feeling:
Hope that helps!
Thanks,
Nate