Cannibalism Without Consequence

[Mageziya]

I wish this was a trait

Curiously, this is an IRL trait. Cannibalism was actually rampant throughout human history, and resistances to prions like the one that causes kuru became so important to survival due to how common cannibalism was that virtually every human race developed some form of resistance trait. Any time the trait was lost (such as apparently was the case with Japan, due to the bottleneck effect that tends to happen with founding island populations), a sufficient replacement quickly developed.

Thing is, as human civilization developed, cannibalism became less and less frequent, thus a resistance to prions became less critical to survival of people. Since it was no longer critical to survival, resistance to prions was no longer actively selected for, permitting for the existence of people especially vulnerable to prions. That said, as a holdover from these cannibalistic days, many people carry an assumed resistance to prions. This is also likely why bovine spongiform encephalopathy (mad cow disease, a prions based disease that can afflict humans) didn't really cause as big of problems as people thought it would. We're descended from cannibals. All of us. Enjoy that thought.

Thus, immunity to prions would actually work as a trait with real-life basis. It also probably won't ever be added to the game since cannibalism is pretty grody and not permitting it is probably a good idea.