Scales of Eberron
Dragonmarks are a sort of magical birthmark that started appearing on certain races across Eberron over a thousand years ago. Some say that they are physical manifestations of the Draconic Prophecy. Dragonmarks are heriditary typically appearing in the bearer’s adolescence as they pass through puberty, however this is not exclusively the case.
In game terms, characters can take a special Feat that represents the fact that they have manifested a Dragonmark. These Feats grant certain powers and allow characters access to specific rituals.