When you take the flower from Iris von Everec, in her mansion, you succesfully free the dog's and the cat's soul (you know them, the guards of the house).
Now, this is the interesting part. They thank you by telling you a very important thing: "Seek salvation in glass that can't be broken". Then, when you meet Gaunter O'Dimm and Olgierd next to the cave, at the end of the expansion, if you choose to help him, Gaunter will tell you a riddle. Now, if you've got that ending (unfortunately, i didn't get it), you know that you need to find the monster in the water. . . water . . . "glass that can't be broken".
So basically, the spirits from Iris' mansion helped you defeat Gaunter.
I don't know if everybody knows that or very few people observed this, but I've never heard anyone talking about this.