Escape from the Crystal Moon

From the introduction:

This adventure is designed to give a party of adventurers enough experience to advance them one level, but this is contingent on the party being in the required level range, of the appropriate party size, and dealing with most or all of the monsters in the adventure. You may also choose to run this adventure using the milestone leveling format, at which point the party will simply gain a level up at the end of the story.