From the publisher's website:
A druid in a small frontier town at the edge of the tundra is gathering stalwart companions for a trading venture across the ice. Only the bravest need apply, he says, for survival in this harsh environment is not easy. But is there more to his venture than he lets on? What's a druid doing in the trading business? Who is his mysterious sorcerer client? Drop this free online adventure by Eric Cagle into a subarctic area of your campaign world. Suitable for four 7th-level characters.
Five years ago, the druid Agarathar set forth on an exploratory mission, following a tip he had received from some of the nomads who wandered the tundra. He charted his way along the icy shorelines, seeking out a wizened sorcerer who was said to live on a frozen lake. After a grueling month of travel, Agarathar managed to locate the home of the sorcerer, which was actually fashioned out of a gigantic iceberg in the middle of a frozen arctic lake. In this icy fortress, he found the fabled sorcerer Zilrus, who was delighted to have some company in his cold and isolated realm. The two became fast friends, and the druid continued to visit the sorcerer for a few years. But the sorcerer was not what he seemed, and the relationship turned sour when the druid announced his upcoming relocation. In retaliation, Zilrus stole that which was most dear to the druid, telling him that it would be returned when Agarathar returned with the specified ransom. To regain that which he has lost, Agarathar must deliver a shipment of goods and food to the sorcerer's iceberg-fortress. But he will need help. . . .