Hard to imagine this being your first map, I found it very impressive and fun overall!
Graphics
Very nice brushwork overall. Lots of rounded columns, roofs, etc.. Some minor texture alignment problems, but nothing fancy. My biggest gripe (and it isn't that big!) would be with the lighting. All the rounded items I mentioned could use some phong shading, I feel it was made very specifically for this purpose. And there were some areas that were just black, and could have used some ambient lighting. I love the choice of skybox, its red contrasts very well with the overall bluish theme.
I also like the little tidbits with the fallen soldiers and the shabby look of the "palace" in some places.
Mechanics
I liked the jump portals, the particle effect makes them clearly visible. They weren't used to great effect, but they're not useless either.
I was very impressed by the "energy pipes" effect and the crystals draining the pipes, a good addition!
Difficulty
I found it pretty easy, even the end boss.