Sacred 2: Fallen Angel game director Daniel Dumont tells us about creating the "fog monster" quest in a new entry to the game's blog on IGN.
When the fog monster is beaten, you'll find an item that can be use to patch the hole in the distribution box. You can do this, but you don't have to. Depending on whether you're playing on the Light or the Shadow side, you can either patch the hole or throw the rusty old item away.
If you patch the hole on the Light path, people will sleep less afterwards and they will therefore have more time to wage the wars they love so much. If you throw the item away on the Shadow path, you'll simply travel on to the next desert region. Here you'll encounter more interesting creatures with different problems, and at the end of this region there's the next boss opponent waiting for you.