Ulfric Longbeard is an undead Fremenik sailor. His vessel was one of several that transported treasure. However, some of the treasure was cursed, causing the ships to crash. Ulfric's ship crashed into a cavern, and he and his crew perished there.
Sven the Helmsman, one of Ulfric's crew, drew a map, which eventually made its way to his grandson Olaf Hradson. Olaf failed to find the treasure and, believing the map to be cursed, gave it to an adventurer who helped him. The adventurer found the cavern and located the treasure. When they tried to take it, Ulfric rose from the dead to defend it.
He acts as the final boss during Olaf's Quest. He is fairly easy to defeat due to his low and inaccurate hits. Protect from Melee can be used to reduce the damage from his attacks, or he can be safespotted by using his gravestone as a barrier.