“ A race of beings actually IS invunerable while in adolecence. They age, but cannot be killed. A miniority of the race (1 in 20) does not become invunerable, but rather becomes immortal at some point in thier adolecence, and ceases aging while being vunerable to death in all the normal ways. Another minority (also 1 in 20) Permanatly becomes invunerable after adolecence, but ages twice as fast as the race normally does. There is no known way to test for which of the three traits an individual manifests and the three traits cannot mix, as they are tied to the same gene, as it were.”
“ As you emerge from the shop in the alleyway, not-too-distant clanging and stamping makes you wary. Further investigation reveals a massive Balgrian protest march flooding the main street, banners roaring about the inhuman conditions in which this ethnic group is forced to live. City guards stand helplessly by, beating up the odd protestor, but unable to hold back the flow. Onlookers throw vegetables at the Balgrians, and shout abuse.”
“ A village where everyone goes blind sometime during puberty. What could be causing this? Perhaps something in their diet. Or some malignant gene. How would an entire village where only young childen can see function?”