The Pisaca in the dungeon in the Duke's Archives are actually humans captured by the Channelers for Seath's experiments, explaining why these creatures drop a fairly consistent supply of Humanity. Two in particular each drop a different Miracle. When considering the fact that Rhea of Thorolund's Hollow can be found in the dungeon after all her Miracles are purchased, and the fact a corpse in the dungeon is wearing the Maiden Set that Rhea wears, it can be speculated that the two docile Pisacas are former Maidens, and that Rhea was going to receive the same fate.