Here is a Map of the location for this collection:
https://photos.app.goo.gl/ewXb6wsdPYh3LFRr5
This is the general area of where they appear. Some are behind columns and 1 I found in a light. So you may have to constantly run down a hall, look back and move on. You best option is to find and get both perm invis and invis vs undead. Then you can wander the whole area. Except nameds.