So for the tier 3 fog immortality...would things like being set on fire, decapitation, or drowning count as destroying the heart or brain? Or do one of those organs actually need to be pierced/pulled out/expressly destroyed?

Basically, I'm curious as to the limitations in general, but I have a particularly biased curiosity about how this would work with a nymph's fatal fire weakness. Because in the event they were just straight up torched, presumably the fire would reach their heart and brain at some point?

On a related note, does the "or" mean that we get to pick one organ over the other as a fatal weak point or do they get both no matter what?