Book of the Long Lost Metallic Dragon

After stumbling upon a book of spells that seems to be older than the dawn of man, written in an ink you cannot recognize, on pages made of some arcane material the making of which must have been a process lost to time, you find yourself drawn to it in a way that taps into your very soul.

Blood of the Dragon

At 2nd Level, when you first find this book, you open the cover and begin to read the foreword written by the Dragon who wrote these spells.  You are infused with the blood of this Dragon, pick the color of the Metallic Dragon who has written the book, you gain the benefits described: Gold, Silver, Bronze, Brass, Copper.

Similar to the feat Aberrant Dragonmark your spell casting ability for these spells is always Constitution

Expanded Spell List (You learn several spells from the book.  These spells are gained as soon as you have spell slots of the level needed to cast them, and are considered always prepared)

All: Resistance, Feather Fall, Levitate, Fly

At Later Levels you get additional benefits based on your Dragon Color.

Brass Blooded

As you read the book your blood is slowly infused with the magic of a Brass Dragon, you gain access to these spells

Control Flames, Firebolt, Sleep, Scorching Ray, Fireball

Bronze Blooded

As you read the book your blood is slowly infused with the magic of a Bronze Dragon, you gain access to these spells

Gust, Thunderclap, Thunderwave, Gust of Wind, Lightning Bolt

Copper Blooded

As you read the book your blood is slowly infused with the magic of a Copper Dragon, you gain access to these spells

Acid Arrow, Acid Splash, Fog Cloud, Slow, Stinking Cloud

Gold Blooded

As you read the book your blood is slowly infused with the magic of a Gold Dragon, you gain access to these spells

Control Flames, Create Bonfire, Ray of Enfeeblement, Fire Shield, Wall of Fire

Silver Blooded

As you read the book your blood is slowly infused with the magic of a Silver Dragon, you gain access to these spells

Vicious Mockery, Disguise Self, Detect Magic, Invisibility, Sending

Draconic Presence

You are always aware of the presence of your Dragon Companion.  It whispers in your ear, sometimes constantly, incessantly.  It yearns to live again, and it asks your help in exchange for favors, spells, information.

You learn the language Draconic.

You gain proficiency with a Disguise Kit.

Breath of the Dragon

Start at level 6 you gain the ability to cast Dragon's Breath on yourself, choosing the type of damage associated with your dragon color (Gold and Brass: Fire, Silver: Cold, Bronze: Lightning, Copper: Acid). 

You cast this spell using a spell slot level equal to your proficiency modifier but without expending a spell slot. 

You may do this a number of times per day equal to your proficiency modifier and regain all uses when you finish a long rest.

Word of the Dragon

Starting at level 10 you gain an additional "Breath Weapon".  Using your Breath of the Dragon charges you may instead cast the spell with the following Breath Weapons but without the normal damage.

Gold: Weakening Breath. Exhale gas in a 15-foot cone. Each creature in that area must succeed on a Strength saving throw against your Draconic DC (8 + Constitution Modifier + Proficiency) or have disadvantage on Strength-based attack rolls, Strength checks, and Strength saving throws until the end of your next turn. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Silver: Paralyzing Breath. Exhale paralyzing gas in a 15-foot cone. Each creature in that area must succeed on a Constitution saving throw against your Draconic DC (8 + Constitution Modifier + Proficiency) or be paralyzed until the end of your next turn. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Bronze: Repulsion Breath. Exhale repulsion energy in a 30-foot cone. Each creature in that area must succeed on a Strength saving throw against your Draconic DC (8 + Constitution Modifier + Proficiency). On a failed save, the creature is pushed 15 feet away from you.

Brass: Sleep Breath. Exhale sleep gas in a 30-foot cone. Each creature in that area must succeed on a Constitution saving throw against your Draconic DC (8 + Constitution Modifier + Proficiency) or fall unconscious until the end of your next turn. This effect ends for a creature if the creature takes damage or someone uses an action to wake it.

Copper: Slowing Breath. Exhale gas in a 15-foot cone. Each creature in that area must succeed on a Constitution saving throw against your Draconic DC (8 + Constitution Modifier + Proficiency). On a failed save, the creature can't use reactions, its speed is halved, and it can't make more than one attack on its turn. In addition, the creature can use either an action or a bonus action on its turn, but not both. These effects last until the end of your next turn. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself with a successful save.

Dragonreborn

During the first long rest after you gain level 14 you are visited by the spirit of the Dragon who wrote your book.  Gifting you a sliver of its own soul and magical essence the dragon strikes a deal with you to return to the world as a part of you.

You grow and morph overnight, scales sprouting on your skin in patches, the scales of the dragon itself, you grow slightly, not enough to change your size but enough to notice, your face grows slightly draconic compared to its previous shape, and your eyes form vertical slits, the eyes of the dragon.

Increase your Constitution score by 1, to a maximum of 20.

You gain resistance to the damage type associated with your dragon.

Your base AC becomes 13 + Dexmod when you aren't wearing armor, from the scales.

And finally, you grow a tail that does not function as a prehensile tail and does not have any actions associated with it.  Some may grow vestigial wings, at DM discretion.