I think we've figured out most of it. Basically, the people who build the house had a husband who was a wizard-adventurer who went all over the world gathering the components to make himself into a lich. Then his wife barged in after he drank the potion to kill himself but before he could put his soul into the box, ruining everything. He ended up as a ghoul and killed her, and she started haunting the place.

Then, several generations of their children and grandchildren moved in and went crazy from the ghosts and killed each other, making the house more and more haunted.

Finally, Aldin showed up and started trying to restore the place, but he broke into the basement and let out the ghouls who turned him into a ghoul and now he's ghouling it up all over the land.