Tjorkil Ylvarrik

Tjorkil is something of a blank slate. His function is to lead a rival group of adventurers who might encounter the PC party from time to time. Eventually he will succeed his father as jarl of Arvaald. He can grow into a hated enemy of the PCs and become a major villain, he can be a rival who opposes the PCs in a limited context but joins with them against dangerous outsiders, or he can become a friend.
Tjorkil and his rival band of adventurers should encounter the PCs in some tense situations early on. If the PCs are friendly and seek peaceful cooperation on these occasions, Tjorkil will become a friend. If the PCs are ruthless (fight first and ask questions later) and regard Tjorkil as an enemy, he will be an enemy. If the PCs pursue a middle path, Tjorkil will remain more ambivalent, but if he is treated with honor, even despite a rivalry, when real enemies appear from outside, Tjorkil will fight alongside the PCs until the danger has subsided.