Magic Missile Prodigy

Magic Missile is a favored staple of many arcane spell casters and an example of raw magical force. Thus, it is no wonder that a cabal of arcane spell casters focuses their studies on this spell, determined to perfect its casting technique above all others. As these spell casters obsessively explore Magic Missile’s secrets and press its boundaries, every rune and magical symbol of the spell becomes inexorably etched upon their minds.

However, you were born with an innate understanding of this particular spell, that of which goes beyond what studies have been able to find, with being able to create new abilities  that let you alter and manipulate the spell's effects as your raw arcane abilities grow. 

Innate Magic Missile

You learn the spell magic missile, if you do not know it already. Additionally, you can cast magic missile at its lowest level a number of times equal to your Charisma modifier. You regain all expended uses when you complete a long rest.

Beginning at 14th level, you can use this ability an unlimited number of times.

Missile Salvo

When you cast the magic missile spell, you fire 1 additional missile, as if the spell was cast using a higher level spell slot. The additional number of missiles increases by 1 at 6th level (2 additional missiles), 10th level (3 additional missiles), and 14th level (4 additional missiles).

Missile Aegis

Starting at 6th level, you can cast magic missile in a tight orbit around you, creating a deadly aegis from your foes which lasts for up to 10 minutes. You gain a bonus to your Armor Class equal to the number of missiles orbiting you, which begins as the number of missiles fired, up to a maximum bonus of +6.
When a hostile creature ends its turn within 5 feet of you, a single missile strikes it, dealing damage as normal and decreasing the number of missiles orbiting you. Additionally, when you cast magic missile, you can add some or all of the missiles orbiting you to the spell, decreasing the missiles orbiting you by the number used.
Once you use this ability, you can’t use it again until you finish a short or long rest.

Missile Chaff

By 14th level, you’ve learned how to use magic missile to overcome your most powerful fellow spellcasters. When you see a creature within 60 feet of you casting a spell, you can use your reaction to cast magic missile, with all missiles targeting that creature. The creature must make a single Constitution saving throw as a result of the total damage dealt to maintain concentration while casting the spell, even if the spell wouldn’t normally require concentration. The spell fails and has no effect if the creature loses concentration.

Missile Battery Bombardment

At 18th level, you have reached the pinnacle of your power with Magic Missile. With an action, you can spend 7 sorcery points to disperse into a swarm of magic missiles, flying to a spot you can see within 120 feet. Each creature in a 40 foot radius sphere centered on that point must make a Dexterity saving through. A creature takes 20d4 force damage and is pushed back 15 feet and knocked prone on a failed save or half as much damage and is not pushed and knocked prone on a successful one.

Once you use this feature, you can’t use it again until you finish a long rest.