I've given up tiptoeing around perceived shortcomings in this song and I'm going to re-rank it with a 10. It's stuck ever since I first heard it and shows no signs of going away.
I'm not one to go looking for full-on 'heaviness' or speed in a song, but Montsegur really does have some clout. There's a few aspects musically that particularly appeal. The ascending patterns in the guitar parts, which then switch to patterns of descending notes in the chorus, at a time when Bruce's voice is soaring high and stretching his ability, stand out. It gives me the impression of toiling uphill, but also faltering or slipping back, too. To me, it fits the image of fanatically striving to ascend to an impossible ideal, as per the Cathar martyrs. I can also visualise an image of wave after wave of beseigers striving to take the mountain top fortress. The overall heaviness suggests an unstoppable onslaught, be it the attackers, or the course of time sweeping along and wearing down the ideals of any given period, rendering them worthless eventually.
Secondly, the instrumental part in the middle is incredibly effective, and other than the chorus, was my biggest hook into this song. The solo itself is a fairly standard offering of the 'messy Janick' chaotic variety, although it also spirals up before crashing down, but is followed by what I can only think to describe as a double bridge. The first one alone would be sufficient to lead very nicely back into a verse or chorus (not sure if it's long enough, though), but they then build the song up into a second bridge, increasing anticipation for the chorus. This itself swells in magnitude with the harmony in the second half. That's a big-impact buildup in a comparatively short song, it's more the sort of device you'd expect in a longer epic.
The happy clappy version of the chorus at the end really does sound overly cheery and badly misplaced, especially with the accompanying lyrics, but then I think that's the point. It's like a glorious, triumphant fanfare, celebrating...the completely pointless, horrific deaths of 200 people. Hurrah! To followers of the Cathar faith, the martyrdom may have been achieving their ultimate goal. To the present-day thinker it was a needless atrocity and tragedy.
Subject wise, Montsegur isn't limited to a rant about the stupidity of the past. 'Still burning heretics under our skies' compares atrocities of the past to the present. Personally, it gets me thinking about other strong beliefs and doctrines, in addition to religion, that people will cling to to the extreme of harming others.
I actually feel quite a lot went into this song. Rather than it cribbing the riff from Fallen Angel, it takes an incomplete idea further. Then there's the harmony in the second part of the bridge, which sounds not at all unlike a melody from a song by White Spirit, Janick's old band. Plus we have what I assume is Bruce's historical input.