Age.
Young dragonborn grow quickly. They walk hours after hatching, attain the size and development of a 10-year-old human child by the age of 3, and reach adulthood by 15. They live to be around 80.
Alignment.
Dragonborn tend to extremes, making a conscious choice for one side or the other in the cosmic war between good and evil (represented by Bahamut and Tiamat, respectively). Most dragonborn are good, but those who side with Tiamat can be terrible villains.
Size.
Dragonborn are taller and heavier than humans, standing well over 6 feet tall and averaging almost 250 pounds. Your size is Medium.
Draconic Ancestry.
You have draconic ancestry. Choose one type of dragon from the Draconic Ancestry table. Your breath weapon and damage resistance are determined by the dragon type, as shown in the table.
Breath Weapon.
You can use your action to exhale destructive energy. Your draconic ancestry determines the size, shape, and damage type of the exhalation.
When you use your breath weapon, each creature in the area of the exhalation must make a saving throw, the type of which is determined by your draconic ancestry. The DC for this saving throw equals 8 + your Constitution modifier + your proficiency bonus. A creature takes 2d6 damage on a failed save, and half as much damage on a successful one. The damage increases to 3d6 at 6th level, 4d6 at 11th level, and 5d6 at 16th level.
After you use your breath weapon, you can't use it again until you complete a short or long rest.
Vengeful Assault.
When you take damage from a creature in range of a weapon you are wielding, you can use your reaction to make an attack with the weapon against that creature. Once you use this trait, you can't do so again until you finish a short or long rest.
Darkvision.
You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in darkness, only shades of gray.
Languages. All Dragonborn can perfectly understand Draconic, and can speak Common to varying degrees.