I'm not there yet. I'm thinking at this preliminary stage about what lore to potentially incorporate, or possibilities for characters or monsters or what have you.
I think you might enjoy looking into Castle Rising in Kings Lynne, Norfolk England to include in your fiction.
It's a 12th century English castle that I've visited a couple of times including today.
Queen Isabella of France married King Edward the ll. King Edward was openly homosexual which annoyed his Queen so she arranged for him to be murdered. This was achieved by (I'm not making this up) a red hot poker being pushed in Edward the ll's anus.
Seriously.
A lot of people assume this was her revenge for him being gay but there was another reason that brutal form of murder was chosen. It would leave no obvious marks on a King who'd been murdered so harder to prove who the culprit was.
Edward the ll's son, Edward the lll worked out what had happened and banished Isabella to Castle Rising to live out her years confined but also in luxury.
Reports were she went mad. Current folklore is that the castle is haunted by her wailings on the upper parts of the castle, a woman and child in period clothing have been seen walking down the grand stone staircase by occasional tourists and a as yet unexplained 'tapping' sound on the windows can be heard. I was filming there a few nights ago for a Norfolk paranormal investigation group and although we didn't see anything strange, the tapping sounds were loud.
I've worked before with Chris Halton, the gentleman who's produced and is presenting this video of Castle Rising. I think this would be a great location to incorporate into an Evil Dead story.