The Devilry Encyclopedia is a Magic Book which can be found in this game. It has a very long preparation time and when casted it turns any creature into an Evil Warlock. This can be used to get the warlock's Occult Omnibus. However caution is advised as the Evil Warlock hits pretty hard with his missiles and is relatively hard to kill. This might be used to turn something like a lich or satan into an easier creature but im not sure.