Go through the tomb. Traps all triggered, skeleton bones everywhere.
Find coin trap, trigger it. Dispel annihilation void with nat 20.
Find source of voice and skeletons. Melinoe and her brothers, trapped on the side of a barrier. Party passes by.
Go through puzzles. Miss int chest. Get some masterwork tools and learn the tomb used to be under a disguising monastery which abandoned it millennia ago.
End at room with guardians somehow still alive after 3k years.