I've read the scroll about a weapon lying in darkness but I thought it's somewhere else on the level, which at that point was still mostly unexplored. So I did following:
First, I always removed torches from sconces throughout the game (or put a torch in an empty one), just to be sure. It paid off several times. So I removed the one in the Hall of Designers too without thinking about it too much.
Then I accidentaly (!) stopped in front of the altar to check my map for a possible hiding place of the Weapon. While checking, my Light spell wore off and the Weapon appeared in front of me
Mind you, the Light spell last quite long and I would've closed the map in a few seconds, so it was really incredible. If it wasn't for this crazy coincidence, I might have been still running around lvl 11 trying to access some secret cache with the Weapon
)
And what's even funnier, I first thought the Weapon appeared because I waited long enough
(remember, there's a Iron Door somewhere that opens only when you wait, so I thought it's the same mechanics). Only when I read this thread I did a facepalm. Double facepalm
