From the introduction:
This adventure can be can be easily customized to a party of any size or level, or run as a level 10 adventure for 5 players. It can work as a small side adventure in an existing campaign, as a standalone one-shot, or the start of a new adventure. Use the links to the tools in their relevant section to customize the adventure to your party.
The party is traveling through the wilderness between adventures or on their way to their next objective.
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The party encounters a goblin explorer. The goblin travels alone, mapping the regions he passes through. His maps are mostly inaccurate. Notably, he has a city marked about a day's walk in the direction the party came from. There was no city there, but he insists he saw it when he passed through a few days before.