The Dragon Student

Source: Children of the Dragon

The Dragon Student is an unusual patron, as you are the one teaching it. Your power comes from your dragon student, but it is you who helps it harness this awesome power. Technically this power comes from lo, the dragon primordial of creation, who gifted this power as an otherworldly patron. But it's your dragon student who grants it to you directly. This is why you are more warlock than wizard.

You are a Dragon Master, a young student of the Darastrix Academy. At a young age you were bonded with a dragon wyrmling, entrusted to you by its dragon parent.
Even though you are a student, you are a master in your own right to your dragon wyrmling, as you teach it to harness its power. Due to the bonding, your wyrmling shares your drive to learn its dragon magic quickly, at the cost of other aspects of its draconic might being weakened.
Although you are technically a wizard, the bond that you have made with your dragon has granted you access to its awesome dragon magic, but in exchange your own studies towards the arcane have been limited. Moreover, due to your bond you share some of the dragon's temperament, and you are inclined to actively seek out the joy of adventure. Now you and your dragon wyrmling bonded partner go out on adventures, as you seek to put the power of dragon magic into practice, regardless of your young age.
Most Dragon Masters are human, but half dragons have been known to teach siblings. Celestial, gem, and steel dragons don't send their young to become dragon students, due to their secretive nature and strict traditions.
Your magical bond with your dragon companion grants you access to its powerful dragon magic in addition to your own mortal magic. For example, a Bigby's hand would look like a fist when cast by a humanoid, and as a flaming claw when cast by its red dragon student. And even though you still need to study, most of your magical power comes from this bond. As such, Dragon Masters have a saying when it comes to their dragons: You teach me and I teach you.

Dragon Magic

At 1st level, you and your dragon share the same spell slots, and you can both cast your known warlock spells. However the damage type of your eldritch blast, and all spells that your dragon casts (if and when they deal damage), is changed to your chosen dragon's damage type, as listed in the Dragon Student table. Your dragon can cast eldritch blast as a melee spell attack. Your dragon uses your Charisma modifer for its spells, and shares your spell save DC and spell attack modifiers. Only you can maintain concentration on spells you both cast. Your dragon can cast spells without requiring material components, except a material component that has a cost. By expending a spell slot you can summon your dragon into an unoccupied 5-foot-square space within 60 feet of you as an action, but afterwards it gains one level of exhaustion.

You must choose the Pact of the Dragon as your pact at 3rd level, which is a pact that can only be chosen by this subclass.