Forming a bond with a dragon is a long and arduous process. Many would argue it isn't worth the time and trouble. But when done correctly, the tandem cooperation between the dragon and its rider is a force to be reckoned with. They are rare, but dragon riders are elite warriors and not to be trifled with.

Level 3: Rider's Prowess

Learning how to ride a Dragon demands far more than a simple Warhorse. You gain the following benefits.

• You gain proficiency in Animal Handling, and you have advantage on Charisma checks made to interact with monsters of the Dragon type.
• You learn Draconic.
• You have advantage on saving throws made to avoid falling off your mount.
• You can land on your feet if you fall off your mount and descend no more than 10 feet, provided you are not incapacitated.
• You only need to expend 5 feet of movement in order to mount or dismount a creature.

Level 3: Dragon Mount

As an action, you can magically summon the dragon that is bonded to you. It appears in an unoccupied space of your choice within 30 feet of you and uses the Dragon mount statblock. The dragon is Friendly to you and your allies and obeys your commands.

The Dragon in Combat. In combat, the dragon acts during your turn. It can move and use its Reaction on its own, but the only action it takes is the Dodge action unless you take a Bonus Action to command it to take an action in its stat block or some other action. If you have the Incapacitated condition, the dragon acts on its own and isn’t limited to the Dodge action. The dragon can be used as a mount, but it cannot use its flying speed while mounted.

Resurrecting the Dragon. If the dragon mount has died within the last hour, you can take a Magic action to touch the dragon and expend a use of your Second Wind. The dragon returns to life after 1 minute with all its Hit Points restored. Otherwise, you can perform a 1-hour ceremony to resurrect the dragon; this ceremony can be performed as part of a Short or Long Rest.

 

Additionally, upon first gaining the dragon mount and at the end of a long rest, you determine its color. The damage type associated with its color is used for some features from this subclass.

Blue or Bronze

Your Dragon's element is Lightning damage.

Copper or Black

Your Dragon's element is Acid damage.

Gold, Red or Brass

Your Dragon's element is Fire damage.

Green or Steel

Your Dragon's element is Poison damage.

Silver or White

Your Dragon's element is Cold damage.

Level 7: Advanced Training

You and your dragon gain the following benefits.

Dragon Mount. The dragon grows to Large size, and its Strength score increases to 16. You can use the dragon as a mount if you are Medium or smaller, but while you’re riding it, the dragon falls at the end of a turn if it’s airborne and the only thing holding it aloft is its Fly Speed.

Tempered Fangs. The dragon’s Bite attack increases by 1d8 piercing damage (For a total of 2d8 piercing damage), and its Elemental Breath becomes a 30-foot Cone or 60-foot-long, 5-foot-wide line.

Shared Second Wind. When you use your Second Wind to regain Hit Points, the dragon also regains Hit Points equal to the amount you rolled plus your Fighter level, and it regains one use of its Elemental Breath.

Level 10: Twofold Tactics

The bond between you and your dragon mount begins to magically influences you both.

• You gain resistance to the damage type associated with your dragon's color. When you reach 18th level in this class, you also gain immunity to that damage type.
• Once per long rest, the dragon can change its element as a bonus action.

Additionally, the dragon's body adapts to environmental conditioning.

Lithe

The Dragon's body is lithe and built for endurance, granting it the following benefits.

• The Dragon can take the Dodge action as a bonus action, and its movement does not provoke Opportunity Attacks.
• The Dragon's Dexterity score changes to match its Strength score.
• The Dragon has advantage on Dexterity saving throws.

Stout

The Dragon's body is muscular and powerful, granting it the following benefits.

• The Dragon can choose to grapple a target upon a successful hit with its Bite. If the target is already grappled by the Dragon, the target is instead restrained until the Dragon chooses to let go.
• The Dragon's Constitution score changes to match its Strength score.
• The Dragon gains resistance to bludgeoning, piercing, and slashing damage.

Level 15: Expert Training

You and your dragon gain the following benefits.

Superior Dragon Mount. The dragon grows to Huge size, its Strength score increases to 18, and both its Speed and its Fly Speed increase by 10 feet. Additionally, the dragon no longer falls at the end of a turn if airborne while you’re riding it.

Unbreakable Loyalty. The Dragon is immune to the Frightened and Charmed conditions.

Empowered Fangs. The Dragon's Bite deals an extra 1d8 piercing damage (For a total of 3d8 piercing damage). 

Tandem Attack. When you take the Attack action on your turn, you can forego one of your attacks to command the dragon to make one Bite attack. Alternatively, you can forego two of your attacks to command the dragon to use its Elemental Breath. Lastly, when you use your Action Surge, the Dragon can make one Bite attack as a reaction.

Level 18: Unleash the Dragon

You have reached the apex of your bond with your dragon, making you a formidable combination on the battlefield. When you roll initiative, you regain one use of your Second Wind feature, and your Dragon mount regains one use of its Elemental Breath.