Your lineage stems from a dragon progenitor. Choose the kind of dragon from the Draconic Ancestors table. Your choice affects your Breath Weapon and Damage Resistance traits as well as your appearance.

When you take the Attack action on your turn, you can replace one of your attacks with an exhalation of magical energy in either a 15-foot Cone or a 30-foot Line that is 5 feet wide (choose the shape each time). Each creature in that area must make a Dexterity saving throw (DC 8 plus your Constitution modifier and Proficiency Bonus). On a failed save, a creature takes 1d10 damage of the type determined by your Draconic Ancestry trait. On a successful save, a creature takes half as much damage. This damage increases by 1d10 when you reach character levels 5 (2d10), 11 (3d10), and 17 (4d10).

You can use this Breath Weapon a number of times equal to your Proficiency Bonus, and you regain all expended uses when you finish a Long Rest.

You have Resistance to the damage type determined by your Draconic Ancestry trait.

You have Darkvision with a range of 60 feet.

When you are being attacked, you can spend a reaction to deflect the attack with your tail and surprise the attacker, possibly avoiding the attack in the process.

If a creature you can see within 10 feet of you hits you with an attack roll, you can use your reaction to swipe your tail and roll a d8, applying a bonus to your AC equal to the number rolled, potentially causing the attack to miss you.