Very nice, very different sentiment. The flow seems fine to me. I couldn't see anything wrong with it. I have a few punctuation nitpicks for you, though.

stains, marks, and brittle flesh;
stains, marks, and brittle flesh**,**
(The next two lines could not form a new, independent sentence, so the semi-colon is not correct.)

*The immortals can live, and sing forever.

We mortals can live, and die for God.*

Either take out the comma each time before the word "and" or put an extra one in after the second phrase: > The immortals can live and sing forever.

We mortals can live and die for God.

or > The immortals can live, and sing, forever.

We mortals can live, and die, for God.

Thanks again for another great poem,

Cres
Wielder of the Red Pen