This is something I have wanted to do for a long time; make a dungeon that is a haunted house. At least at the start, to make the project easier to write, I will use Tegel Manor as a monster guide, and Ravenscrag castle as the layout maps.

Not all the undead are hostile in this place, for they remain in "life" because of a curse on the castle by a high level Evil Cleric that none living in the castle should rest easy upon death, but instead, rise and return to the castle and resume their old position at the time the curse was laid.

The Evil Cleric Delbart worshipped Myrkul and although he surrounded himself with the dead and dying, he fell in love with a beautiful woman. He came to the castle to ask for her hand in marriage never even suspecting that he might be turned down. The maidens father knew immediately that his daughter did not want to wed the priest, but the rich and power priest tempted the father with lies about the things that would happen when the two houses were joined. After many months of courting, the priest demanded an answer without further delay, threatening the father with death and destruction if he did not answer. The manner with which this was done convinced the father that he would condemn his daughter to violence and horror if he answered yes. The priest was homicidally angry.

The priest killed the father and several knights who were nearby with powerful magic spells. He summoned demons to fight the guards of the castle to win his escape and give him time to use a wish spell the Priest had found. With the wish and the Power of Myrkul, he laid a curse on the building and those within. This curse he pronounce in the hearing of all who watched from the Battlements. They recorded his words and this will form the major clue that that party must use to solve the mystery of the Castle and make it their own.