Unknown Warhammer 40k track

Hey guys, I've been searching for information on this track for about a year:

the link goes straight to mp3 playback on my dropbox

https://dl.dropboxusercontent.com/u/...o%20Mortis.mp3

The case is this: the track is called "Legio Mortis", the music is played by an orchestra with strong percussions. A choir is chanting in latin and the lyrics are centered on Roman Empire or similar impirial entity (distinctive phrase "Legitus maxus primus" can be heard)

During my search I have seen numerous copies of this file, all attributed to Warhammer 40k series. Sometimes the track is labeled "Horus Herecy". However there are no official soundtrack releases that include this piece. By official releases I mean OST's from Dawn of War, Space Marine and Chaos Gate. I am afraid that this track has nothing to do with Warhammer series whatsoever. In that case I am left with almost every movie about Roman empire to search through.

I tried Shazam, I tried googling by pieces of that distinctive Latin lyrics, I tried other what's-that-song services, but all in vain. Hope someone on this forum will help me. All i want to know is the source, the composer and, if it is possible, the correct lyrics.

Many thanks in advance!

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