“ Herbalist in the group mistakes one plant for another and mistakenly poisons the group. Not to death, but pretty darn ill with recurring symptoms until the cause and cure are realized. (Local people may be able to help rather easily. 'You ate Dragon's Rot you fool, looks and smells just like mint except it has these small thistles on the root. Only grow in the Hornwood Forest, that must be where ya got them. Eat this and you will feel better in 4 hours.'”
“ Have a large room that elevates either up or down when triggering a trap. The floor can bring the players to new levels, where a mighty beast roams, or the floor flattens the players into the ceiling or drop into a pit of lava.”
“ After the PCs defeat (or force the rapid retreat of) a villanous necromancer/demon summoner, they discover a book. This book outlines how to summon a demon whose power increases according to the size of the summoning circle used to summon it. And after the PCs examine a map of the country, they find that the layout of the cities and roads match up with the required summoning circle. In fact, the final road that would complete the circle is currently in construction.
With anyone who can find out about the circle and the ritual to summon the demon able to somehow make the final road/line, and destruction of the cities and roads currently in existence out of the question (unless this is an evil campaign- that removes the moral quandary), how are the PCs going to solve this problem?”