It is said that "the First King was a lucky soldier." Seth Trollslayer was that lucky soldier. He took advantage of the fog of a war 'twixt Man & Trolls to place himself on the throne of a small kingdom in the northern mountains and take a beautiful shapeshifting sorceress as his queen.
Now, King Seth has had time to raise a family. All three of his sons are strong, quick, and charismatic young men- perfect leadership material. If only the youngest had the wit and wisdom required to be truly great...
Nevertheless, the youngest son took up the reins of a small company of his father's men- his long time personal arms trainer among them as his Sergeant- and regularly went out to patrol the kingdom's borders.
It was on one such patrol that a messenger arrived from his mother, the Queen, bringing word of the death of his father and 2 older brothers...and ordering his assassination. The word was given while he was away from the camp for...recreation. Alone among the company, the Sergeant was loyal to the young prince, and he died killing off the would-be assassins.
It seems that the family his father "displaced" had one member he didn't know about- the former King's youngest brother- whose lifelong love was the Queen whom Trollslayer married. She ordered her entire family killed to be reunited with the long-lost flame she once thought dead, restoring him to his rightful throne.
The good but dim young Trollslayer knows none of the reasons behind the attempted assassination. He also doesn't really know the way home. Now he seeks his way in the world, his long-term goal to restore himself to the throne his father once held. He is quick to show anyone who is curious the birthmark that graces his left (nether) cheek that marks him as King Trollslayer's Scion, in order to get them to help him regain what he lost, never realizing that his birthmark also marks him for death.