This is a short and rather vague encounter-based adventure involving a dead sphinx... whose ghost persists in asking riddles! His motivation is that he wants his recent demise avenged, and he lures the party with promises about loot left in the last place that he slept.

The idea is that you have the ghostly sphinx accost the party as they are travelling - hence it's easy to slot in anywhere in whatever campaign world you are using. Even as a ghost, the sphinx is far too powerful for a party of the intended level, so this is a good adventure for groups who like to talk and think... or as a lesson to those who fight first and talk later if at all!

After meeting the ghostly sphinx, the party is directed to his lair - a bare cavern - and thence to those responsible for his demise, and those parties who want a fight can have one then, and again as they follow up to a nearby town (use one of your own, or there's the bare outline of one provided).

There's advice on how to run riddle-asking with suggestions about what checks could be made if nobody's good at riddles, and also about how to handle dealing with NPCs, in particular the use of checks to adjust attitude until the NPC is willing to talk or otherwise be helpful - useful to novice DMs (remember, this was originally release about six months after the rules...). There are no maps and minimal location descriptions (if you like such things you'll have to come up with your own), but there are stat blocks for those the party will encounter - even the sphinx although they aren't supposed to fight him. Some will, or you may want to use him again later.

It's a little thin, a step above a mere adventure seed, but with potential to make quite an interesting adventure if you work at it.