“ 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.”
“ A city is being plagued by a swarm of winged mice. The vermin can get anywhere, and they can easily avoid their normal predators by simply flying away from them.”
“ A powerful wizard that the PCs encounter is completely silent. He does not speak and cannot be heard as he moves. Even his spells are silent, but his magic is just as potent.
He has a tendency to summon invisible chairs, place foes in invisible boxes of force, and other 'mime tricks'.”