|A special example of a narrative prefab.|
Can you work out the puzzle above? It has two possible solutions. A narrative prefab like that might take up a big chunk of a level, and wouldn't be that common. Most prefabs will be quite simple and self contained.
I can also place guards at a level exit, or even a boss encounter in a treasure room. The events will still be procedurally generated, so that the boss encounter will be generated from a boss encounter table generating a monster (or group of monsters) appropriate to that level, while treasure will be randomized and placed in a suitable container (maybe a desk or a chest or maybe a corpse).
There are other events, such as graffiti which might give you some knowledge (increase one of your skills if you read it) or could even be a curse! Pages scattered on the floor could be a hint about how to defeat a tough monster (maybe even giving a bonus vs specific monster type), or they could yield a map or some general background info. Strange sounds, odors or monster tracks could reveal what type of monster lurks nearby, giving you an advantage in the next fight (If you found rust monster tracks, how would you prepare?) Can you think of any other kinds of events or encounters I could include? I've been thinking about secret stairs or ladders... or as some people on Rogue Temple suggested the other day perhaps some graves with restless inhabitants.