themightykobold says:
"In the heart of Skull Swamp, the frogmen keep their sanity only through deadly crocodile charioteering. Will your PCs survive the course?"
That's pretty amazing.
If there is something threatening their sanity, then the race would likely be a religious ritual to appease whatever-it-is. Perhaps a dungeon-on-rails? The race maybe involving travel through various dreamscapes, the next of which would depend upon how you resolve the current one? So it would vary by playthrough, but there'd be no backtracking to a previous "room".
"Your chariot careens through the temple, your crocodiles' legs windmilling furiously under the lash, untold piles of loot flashing by as you hone in on the scepter standing on the distant altar. But the temptation proves too much for your warrior and he leans over, sword outstretched to snag a glittering gemstone necklace as it goes past. At the moment of contact you feel the world around you lurch, and an instant of
dislocation ends with your chariot stuck and sinking into the waters of a bog. The world is dark around you. Ahead through the trees is the glitter of a fire and the twisted silhouettes of a cabal of Id Wizards as they gibber and dance around it."