Talk:Corvo's Mask/@comment-8944282-20130613182420/@comment-98.217.139.40-20131209231732

Little bit of Fridge Logic. There are some books you can find in game from Serkonos. One in particular strongly hints that the rat plague was there a very long time before Gristol. Everyone from Serkonos who didn't die were survivors. It would also be a logical assumption that to fight off the plague, the inhabitants built a natural immunity to the it that has been passed down to later generations.

Essentially, Corvo is immune to the Rat Plague. So the use of the mask for anti-plague purposes is unnecessary. It does, however, help protect his identity.