Sosthène here has some pretty nasty scars all over his body, gained from a lifetime of battling/leading a war, but his most prominent scars are some rather large ones on the left side of his face.
Those ones on his face, they were earned when he quite literally died :' ) Got into a fight with the big bad guy that the Gods told him to fight, and when both of them were at the end of their stamina/health, and the fight was getting down to the last hit, he had to block an attack with his sword, and it shattered, letting him get struck across the face so severely that it killed him, as well took out an eye, and cut deep enough to reveal his teeth, even when his mouth is closed. They ended up getting healed by the Big Bad when they revived him and corrupted him to then serve as one of their knights, but never healed enough to undo the damage that was done.
He prefers to keep his scars hidden by his helmet/mask, even though it's slightly shattered over his left eye, but it hides the worst of the scarring at least, poor child.