My players STILL remind me of this litte gaffe I made when I first started DMing. -I- still think it wasn't so big a deal, but then, I wasn't the one busting my head over the problem.
The situation was this. I had a ring of three wishes, which the level 3 PCs were hunting, hidden away in a secret otherworldly dungeon, which was guarding not only the ring, but two very secret, very deadly, very dangerous intellegent weapons, which would be the plot hook for the next two (real time) years of campaigning. All the treasures stored away were guarded by an ancient cult dedicated to never letting the things within become things without. They'd even obatined a young dragon to help them out!
In order for the cult to get in and out of the dungeon, to obtain supplies when needed, to go collect things like, say, dragon eggs... that sort of thing, they constructed what I termed "Sleep Gates"... points at which if you go tio sleep there, your dreams take you to a new destination-- bodily. It was set so that the connection from the normal world the PCs came from would take them to a mysterious foyar... the floor looked like a clock with four more sleep gates that would take the PCs to various parts of the dungeon, and they'd need to obtain things from the various parts in order to progress. It was a fine puzzle, even if I do say so myself. The first sleep gate, in the normal world, appeared to be a normal campsite... it even had a tent. I wanted the players to find this simply enough. The guard dogs they slaughtered to arrive there would be challenege enough, I thought.
And sure enough, they came to the campsite, lost track of the tracks they were following since the cultists gated from that point, and seeing the sun setting on the horizon, they slept at the sleep gate, and arrived at the clock-face foyar.
Now, the way BACK to the normal world I had considered to be an additional challenge, for after they had cleared out the dungeon and all the cultists. It would be a literal leap of faith... the only way back was to jump off the clock into the swirling black mists that surrounded the area. A terrifying and frightening thing that I didn't think they would want to try until all other options left them. I was hoping that first, trying to figure out a way out of this strange dreamlike other world, they'd run out of obvious options and decide to sleep again, thus showing them how to work the sleep gates.
Instead, after finding nothing of interest there, they jumped IMMEDIATELY. They now knew the secret to getting back to their homeworld. The problem was, now they had no idea how to progress further... since upon arriving on the clock, they would no longer "exhaust every option" and thus be forced to go to sleep again. Every time they took a look at the clock room and gave up, they'd just jump off and return to the sunlit realm to think of what to do next. And suddenly, I couldn't concieve of how to get the players to realize what they had to do!
Eventually, they returned to town (two weeks travel in game) and I sighed, and had an NPC own a book containing the answer to the mystery in plain text. What else could I do? But my players STILL harp on me about this "impossible" puzzle I put before them. "Oh, we're supposed to SLEEP on the clock, are we?" is the snarky sarcastic remark I get whenever they encounter a situation they can't immediately think of the answer too.
