Disturbing Video Game Music 196: The Fool's Idol - Demon Souls
Before Dark Souls there was Demon Souls, though in the end the two games are practically identical other than the setting is slightly different. It has been ages since I played this game since much like the games that came after it I think has very much the same problems of it's successors: I don't think these are bad games at all but dang! They nasty hard, demand a lot of memorization, and the repetition is through the roof.
Nevertheless, just like the games afterward this game also has great batch of monsters for you to take on. One of the best is the fight with the Fool's Idol, a mysterious dark maiden whose build up is much more subdued than the average Souls boss and manages to make more of an impact because of this. The slow malevolent music combined with the Fool's Idol's almost casual way of fighting you really makes this a memorable and terrifying boss.
It also helps that she isn't horrendously cheap like 80% of the bosses in these games.