It's unclear whether crafting the plague mask in Kingdom Come: Deliverance 2's new Mysteria Ecclesiae DLC is necessary, but I know I wouldn't want to delve into a plague crypt without a little protection. If you're mindful of the potential consequences of exposing yourself to plague and spreading it around, you'll want to do as the physicians suggest and craft yourself a plague mask as part of the Prevention quest.
The bad news is that Sedletz Monastery has gone into lockdown, its monks into seclusion, and the abbot has ordered you to stay put in the infirmary, and absolutely not go sneaking about investigating the source of the plague. But sneaking about you will go if you want to grab the necessary materials for the plague mask, so make sure to avoid guards and save often.
