Once on a windswept night

Once upon a time, a long, long time ago, there was a traveller...

Our protagonist, a mysterious traveller, wanders the far-off land of Desservir searching for patrons to buy their wares.
Upon hearing about a large annual market in the village of Castella, the traveller decides to set up a stall and try their luck.
Life, however, is not so easy.
After being double-crossed by a goblin and left in the middle of the cold, wet moors to die, the traveller almost gives up hope.
That is, until they stumble upon a mysterious church in the middle of nowhere, and meet the two nuns who attend to it.
What are these two nuns doing on their own, and why is there such a melancholy atmosphere in the air?
The traveller has only one windswept night to uncover these mysteries and learn the truth.