Most dragons have a lair where, due to your accumulation of treasures, you take everything that has value. Sleeping in your lair and under your treasure reduces your rest time to half the time required. Anyone who approaches up to 60 feet from your lair alerts you to possible invaders but does not give the exact location of them. The lair should typically be built in a terrain that fits your ancestry. Having a lair is optional.

Your creature type is considered a dragon.

Although you are a powerful dragon, being in dragon form also has some detriments. While in dragon form you can not wield weapons or use armor and must find creative ways to wear rings, hats, and other apparel.

our physiology allows you to make the following unarmed strikes. (Dragon Form)

• Bite. Your bite deals 2d6 + Strength piercing damage.
• Claws. Your claws deal 1d6 + Strength slashing damage.
• Tail. Your tail deals 1d8 + Strength bludgeoning damage.

You have begun to master your innate magical abilities and as such you can as an action polymorph yourself into any medium or small humanoid you have seen. 

This form of Dragon can hold their breath for longer than regular dragons, enough so that they can fly in space for 10-15 minutes. Similar is holding breath in the atmosphere, or underwater. You can hold your breath for around 45 minutes.

Dragons have a natural affinity for gold and treasure. Whenever you make a Wisdom (Perception) or an Intelligence (Investigation) check related to searching for gold or treasure, you are considered proficient in that skill and add double your proficiency bonus to the check, instead of your normal proficiency bonus. You also have the flaw "Inherent Greed: whenever you see treasure, you have a compulsion to grab it and claim it"

You have darkvision to 60 feet. 

As a bonus action you let out a bellowing Roar. Creatures of your choice within 15 ft of you that can hear you must succeed on a Wisdom saving throw or be Frightened and take 1d4 Force Damage. The DC of the save equals to 8 + your proficiency bonus + your Constitution modifier. Once you use this trait you can't use it again until you finish a short or long Rest.

You can use your action to unleash your Atomic Breath. It goes in a 5 ft by 30 ft line. When you use your breath weapon, each creature in the area of the exhalation must make a Dexterity saving throw. The DC for this saving throw equals 8 + your Constitution modifier + your proficiency bonus. A creature takes 1d6 Fire damage and 1d6 Force Damage on a failed save, and half as much damage on a successful one. The damage increases to 2d6 Damage at 6th level, 4d6 Damage at 11th level, and 5d6 damage at 16th level. After you use your breath weapon, you can’t use it again until you complete a short or long rest.

You can use your action to unleash your Atomic Strike. The creature in the range of the attack must make a Dexterity saving throw. The DC for this saving throw equals 8 + your Constitution modifier + your proficiency bonus. A creature takes 1d6 Fire damage and 1d6 Force Damage plus whatever melee weapon attack you are combining it with on a failed save, and half as much of the damage added on by Atomic Strike as on a successful one. The damage increases to 2d6 Fire and Force Damage at 6th level, 4d6 Fire and Force Damage at 11th level, and 5d6 Fire and Force Damage at 16th level. You can only use this attack three times per long rest. After you use all slots of Atomic Strike, you can’t use it again until you complete a long rest.

Your Strength score increases by 2, and your Charisma score increases by 1.

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.

Dragonborn are taller and heavier than humans, standing well over 6 feet tall and averaging almost 250 pounds. Your size is Medium.

Your base walking speed is 30 feet.

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.

Draconic Ancestry

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.

You have resistance to the damage type associated with your draconic ancestry.

You can speak, read, and write Common and Draconic. Draconic is thought to be one of the oldest languages and is often used in the study of magic. The language sounds harsh to most other creatures and includes numerous hard consonants and sibilants.