According to Part-3 of the Complete Walkthrough, last 3 steps:

- talk to a coffin to find the Necklace of Death at the third level
- go to the Place of Execution Alvaron
- talk to the skull pile in the north to get the skull
- talk to the skull pile again


I am at the Place of Execution Alvaron, with the identified Necklace of Death, but CANNOT find a "skull pile."

What am I or the walkthrough missing?

I wouldn't call it a "skull pile" and it's not exactly "in the north". See this map and look for "Kathryn Winhold's grave" pointer. And you also need "Libre Necronomicon" to be able to bring Kathryn back.

Thanks.

Also, somehow I missed the map, so thanks again for that.

One question from me too. I have both the neclace of deadh (killed the ghost and took it) and Libre Necronomicon. But when i interact with the Kathryn Winhold's grave nothing happens.

You need to have the quest to speak with Kathryn Winhold's ghost in your quest journal. This quest will be added to your journal after you ask Cardinal Gustapho Letti on how to speak with the dead after giving him the letter from Grandmaster Cristoffer de Malamert.

Once you have the quest, interacting with the grave will have a slightly different message and the skull of Kathryn Winhold will appear in your inventory or on the ground and the ritual can be carried out by interacting with the grave again with the skull, necklace and book in your inventory.

Cool. I haven't been to Cristoffer de Malamert yet.

And if I recall right, for the ritual you need a vial of holy water too