What Terry told me could've been just an imaginative version of what took place or as I said before, a rambling of a drunk kid—but one thing stuck to my mind:
What fucking experiments was this witch in the mountains was doing to gain the dead's powers?
Sure, it was as nonsensical as his other statements but one thing's for sure, the bitch— I mean, the witch probably experimented on live people as much as she did on the dead to somehow understand them. But still, I highly doubt someone who based their healing magic on the "dark arts" or realistically speaking, something they just came up on the fly for a few pesos would be able to understand something that killed off more than 90% of the world's population.
There's a small, small chance that she could stumble upon it like the chances of a chimp typing randomly at a keyboard and somehow producing a famous composer's magnum opus.