A small, primitive village has yet to discover fire, which is a good thing because there are highly flammable (but not otherwise dangerous) gasses in the air. The heroes, blissful in their ignorance, don't know that and think it a wonderful idea to show the locals open flame.
Unbeknownest to the character, he is in the royal bllodline. Suddenly the majority of royals fall ill and die, and the hero is left with the crown, but no experience or idea of what to do.
A Deity of some sort has unleashed a plague of bookworms or something like that in the area. Almost all spellbooks are destroyed, along with bardic and historical books.
A magical stave with two distinct uses. One end is a healing stick, which can heal some quite serious diseases, the other half can be used to inflict those diseases on other people.