SCP Foundation

So, I don't know if this already exists, but the basic concept in my head would be a Thaumiel-Class SCP, that the Foundation uses to capture the souls of every human that dies on Earth, so it can't go to the afterlife, effectively storing them for potential use in emergency situations. (Like, reviving them, or sacrificing them in a ritual to stop a K-Class End-Of-The-World Scenario - there would be many possibilities for use.)

I wouldn't really recommend pursuing the reviving concept as it is rendered mostly pointless by the prominence of 2000 and SCP-001 "The Way it Ends." For the first, the Foundation wouldn't really care about individual souls so much as lives, and a soul storage machine for use during an apocalypse seems like just an add on to 2000 that takes some of the fridge horror out of the concept. The Way it Ends depicted the O5 Council's souls being bound in a contract with Death- a plot element that has existed for a while in tales- which this also comes very close to.

The sacrifice angle has a lot more of a potential to it, though you'd need to take care that it doesn't come off as overly edgy.