The Sun has gone out.
Ordinarily in an emergency we'd send word to the Duke, and he might send word to the King, and an army would gather, and march to the problem...but we don't have time for that. The Sun has gone out, and it's getting cold. In the endless night, frost giants and werewolves prowl, undead rise from their crypts, and worse than that, things are coming out of the mountains.
We need the greatest heroes of the kingdom to head into the dwarven ruins and find the secret of Burning Gold. (You thought the dwarves loved gold because it was shiny? No, it's because they knew how to set it ablaze, to provide light and warmth in the deep places of the earth). Then we need those selfsame heroes to take all the gold they can carry, to light their way through the Shieldwall Mountains to the edge of the World, and to find the place from which the Sun rises. Once there, those mighty warriors and subtle wizards could surely find a way to release Her, or heal Her, or persuade Her to take up her shining shield again.
Unfortunately, the great heroes of the kingdom aren't here. So we're sending you.