Other : The Lux Veritatis Website
In 2003 on the official 'Tomb Raider: The Angel of Darkness' website, there was a sub section dedicated to the order that secondary playable character, Kurtis Trent, was a part of - the Lux Veritatis.

Sadly, there is very little of it left these days and it seemed that it became unplayable very early on, but due to the reporting from fansites back in the day, as well as some web archiving, we're able to piece together what the site was about.
Picture
The orange dot that you see used to flicker, like fire, and upon clicking it, it would load up a puzzle.
The image above shows the front page to the Lux Veritatis page. There is a line of 5 dots, which possibly meant that there were five puzzles to complete, however only the first one is lit up. The line is a Flash image (and therefore doesn't appear anymore) and the dot would flicker. Hovering over it shows that it would load up a page called 'Puzzle 01' - sadly it doesn't work and this is where we turn to pages in the past.
A fansite titled 'Beatrice's Tomb Raider Website' wrote a short news update regarding the LV website, dated 12th October 2002. It reads:
"There is this new kind of game puzzle that Tomb Raider Official Website has just made. Click here to try the game and if you manage to enter the right combinations, you will be able to download an exclusive TR:Angel of Darkness screensaver. Two of the combinations are found on the Tomb Raider Official Website(US) and the last one in the newsletter."
Amazingly, this tells us the type of puzzle that players would've completed, how some of the combinations were provided to help fans out and also what the prize would've been.

Fansite 'TRaider.pl' confirms that a screensaver was given out as a prize for the first puzzle. They suggest, in their post dated 11th October 2002, that the other dots aren't available yet, but interestingly they've included a new picture, which sadly we haven't any proof of what it is - it could possibly be the puzzle page.
Picture
Credit: Traider.pl
It seems that each puzzle would've given out different prizes upon completion.

​Looking at the Web Archive, there doesn't seem to be many pages at all, or maybe many weren't saved. Perhaps the others were meant to open up but the site became forgotten about.

​From this listing, we can see that there are two screensavers on offer: standard and lite <- and they can still be downloaded from the original links. If you want to find out which screensaver it is before downloading, see here.
Sources:
  • http://web.archive.org/web/20031001220323/http://www.tombraider.com/luxveritatis/
  • http://web.archive.org/web/20021201101216/http://www.geocities.com/btrsite/tomb/home.htm
  • http://web.archive.org/web/20031014195448/http://www.traider.pl:80/archi.php?B=trpl&Rok=2002&Miech=10