Touch of the Shadowfell

Similar to real dragons, when a dragonborn stays to long or is born in the Shadowfell they are changed. Their scales become dark almost black and their breath weapon is molded into a shadowy version of it self. Their breath weapon becomes Shadow Breath with this addition to its original function: A humanoid CR of your character level or lower is reduced to 0 hit points by this damage dies, and an undead shadow rises from its corpse and acts immediately after the dragon in the initiative count. This shadow uses it original stats with half its max HP.