From GameWatcher: “In between avoiding the Inquisition and numerous swarms of rats, A Plague Tale: Innocence does give players a couple of moments of respite. Its during one such moment that you can complete its The Tomb achievement.
Heres everything you need to know about how to complete A Plague Tale: Innocences The Tomb achievement.”
Source: N4G PC A Plague Tale: Innocence – The Tomb Achievement Guide