The Beasts of Burden quest is available from Marburg. It is recommended as a Level 2 quest.
The village of Marburg lies within dense forest to the sourt of the River Stir. It is an unenviable location, and has paid the price for its proximity to the menacing trees several times over the last hundred years. "The Sacking of Marburg is as common as autumn winds" goes the saying around these parts. This dour outlook has spread to the residents of the hamlet, who all view strangers with suspicion and are never particularly welcoming.
On this occasion your party's arrival is noticed with uncharacteristic interest. The curious villagers all look rather gaunt - confirming rumours that harvests have been meagre over the laster few seasons in this part of the Old World. As the warriors gather in the common room of the village's solitary inn, they are approached by the miller. He doffs his cap and humbly seeks permission to take a seat at the adventurers' table.
"Greetings, strangers. You look like the kind of fold that finds things for a price," says the miller. "I'm missing a donkey - goes by the name of Old Nell. She's a mangy old thing to be sure, but without her the village would starve. There ain't no other beast like her for leagues. We need her back before the next Backertag."
The miller momentarily stops to check your party is taking it all in. "I can't promise much of a reward, but I do have something of value if you find Old Nell. Also," - he leans in closer at this point, keen not to let the inn's other customers hear - "she was taken by spiders, down into their lair, so they tell me. There's more than just my donkey and cobwebs down in that cave." At this point he leans in further and reduces his voice to a whisper, "there's treasure down there too." He sits upright again.
"Now, I know what you're thinking, but I can tell you that Old Nell isn't dead. Not yet, anyway. She went missing last night and those things don't eat straight away. Ask the thatcher about his wie if you don't believe me..."
With that the miller stands, "by Backertag if you want the reward - day after tomorrow," he concludes.
Looks like your party has an ass to find.