The fight up the treacherous rocks of Graeden leads to Gabriel's Tower. Within the tower, you must locate the key which unlocks the secret tunnel to the Castle of Pain and Sorrows. The castle is heavily fortified by Mordred's forces. The evil critters that have infested the area are overwhelming.
Finally reaching the Castle of Pain and Sorrows, we learn that the castle's lower dungeons hold many Quest Knights captured during their search for the Holy Grail. The Quest Knights must be freed, and the Minister of Evil must be destroyed in order to reveal the Scroll of Diablo. Once the lower region of the castle is cleared, Merlin teleports our hero to the upper towers of the castle. Here lurk the strongest of the castle guardians, where the past and future come together, and twisted and perverse magic empower the guardians of Mordred. The face-off with Mordred and his guardians proves much more frightening than the earlier nightmare.