Offer to wash his clothes.

Remembering last night, you suspect that Ulfric's need to wash may have something to do with the smell of cum you noticed when you woke this morning. You also remember that he was still wearing his underwear last night. He'll certainly need his things washed.

"Do you want me to wash your clothes, sir?" you ask, hoping he doesn't suspect you know they need to be and why.

"Err...yes" he says, his tone a little uncertain, something quite unusual for him as he usually speak with complete confidence

You nod dutifully and collect his things. You note that he has already brought a change of clothes with him for after his wash. You head upstream to find somewhere to wash the clothes. You come upon a gravely river bank which is shallow enough to wash the clothes. There's even a large flat rock you lay them out on to dry afterwards. You start with his leggings and tunic, soaking them in the fresh clear water and scrubbing out the various stains as best you can. Finally you come to his underwear.

The white linen garment is pretty similar to a pair of modern boxers, only longer in the legs and with a drawstring to hold them tight rather than elastic. You turn them inside out and sure enough there is a noticeably darker patch on the front. You hold them up to your nose and inhale, filling your lungs with a deep, musky aroma of cum and sweat. It's intoxicating and immediately your cock springs to attention.

The frustration you felt all last night, sleeping next to Ulfric boils inside you and you just have to release it. You pull out your cock and wrap Ulfric's underwear around it. The cloth is soft, good quality, but the biggest appeal is knowing that Ulfric's cock has touched this same garment. You rub your hand along the length of your manhood, vigorously, enjoying the feel of the cloth sliding along your foreskin. With a final twisting pull, you shoot your load to join the now dry load left by Ulfric. There's something deeply satisfying about thinking about your cum mixing together in the cloth. If you didn't have to return them, you'd be tempted to keep them for future use, but he's certain to miss them. Instead, you wash them thoroughly and put them to dry alongside your masters other clothes.

Once everything is dry, you neatly fold everything and head back to camp.