There's an interesting banquet/party mansion in Jack Vance's The Green Pearl. I'm a little distant from it right now but it seems there could have been undead involved. Or maybe just death. It's a cool concept, herded into a party, and then you're ok??? except for all the ghosts. What are they eating? Why are they celebrating? Is this a special event or do these ghosts do this all the time. Are the adventurers recruits? Are they wanted around the table or on the table (as food). Just a little bit of Hansel and Gretel there. Are the ghosts a cover for something really nefarious going on. Upstaris or in the dungeon?

The Jack Vance book is the second book of the Lyonesse trilogy. I recommend the whole trilogy. Some of Vance's best fantasy work. Lyonesse and The Dying Earth. I think The Dying Earth is a little darker. In The Dying Earth even the protagonists are questionable.

If there are ghosts at the banquet maybe there could be skeletons in the closet. (get it?) Bats in the belfry. Some kind of vampire keeping the bats as pets upstairs. The ghosts don't let you go upstairs (for the party's safety). But they let you go down into the dungeon. After you survive what's down there and find something maybe you can go upstairs and fight the big bad. Now what kind of undead inhabits a dungeon? I'm just throwing stuff out there. Maybe some of this stuff will match a gear in your head.