The Curse Collector

Walkthrough

Talk to Zon-Fobun and receive a Cursepaper (key item).
Go to Beadeaux and proceed to one of the sets of machines: you need to visit an Afflictor (which Curses whoever comes near it, unless they are currently Silenced) and Mute (which Silences whoever touches it). So it is important to get cursed first, by coming near the Afflictor, and then touch the Mute to become silenced.

The first, and easiest, set of machines: Go straight in when entering Beadeaux, then turn left (go north) when you reach the wall at F-7. Go north to the wall in F-6, then due east to H-6. From here head south and you'll find yourself going into a cave that leads down. Take that down until it exits at H-7 on the lower map. Go west, south, and west again until you near the glowing red Afflictor in G-8. This will curse you, dramatically lowering your maximum HP and MP, as well as your running speed.
Now head back east and then take your first turn north all the way to G-7 where you will find the Mute. Touch it and you will become silenced, so that you now have both the curses on the Cursepaper.
Return to Zon-Fobun and talk to him; he will gladly take the Cursepaper and provide your reward of a Poison Cesti.

Note: It is recommended that you complete the quest Beadeaux Smog at the same time.
Note 2: There is no in-game confirmation upon touching either machine; this is intentional and you will still be rewarded upon returning with both curses.