Dragons are an inherently magical creature, much like the land of Zerith itself. If a dragon chooses to, they can impart some of their inherent magic through a Dragon Mark.
When injured by a dragon, the inherent energy means it never quite heals right, and will ALWAYS scar. The scar cannot be hidden, healed, even with magic.
A Dragon’s Mark is given benevolently, with purpose, and is a great honor. The dragon slowly carves the mark on the recipients skin, careful to not draw blood. It takes hours, sometimes days (with breaks) to inscribe the mark. When gifted this way, the magic of the mark can confer great benefits to it’s bearer, though there is often stigma associated with the mark as well.
Conversely, being injured by a dragon will leave a person scarred for life, with no boon benefit to offset it. It’s a scar you cannot heal, or hide. If you’re lucky, it’s somewhere hidden by clothing.
Excerpt from “The Origins of Magical Beasts”, Rev. 6 Year 703, by Stillwell Inkblazer