Dragonic Link

Some Fighters have a special Link to a Dragon. This can happen trough the Blessing of a Dragon, inheritage of Dragon ancestors or some similar situation. Trough this Link the fighter gets the abillity to cast acertain spells.

Draconic Magic

On 3rd Level, when you choose this Archetype your Draconic Link establishes itself and comes to the surface. When you gain this feature at level 3, you learn Dracoonic, also you can choose and learn one word in the in the forgotten Old Language of Dragon kind, which can only be used to tell the truth. Speaking this word makes you able to cast Magic.

You can choose another of these words at level 7,10,15 and 18 giving you the ability to cast the spells related to that word.

adurna

Te word adurna means Water.

brisingr

The word brisingr means Fire.

deloi

The word deloi means earth.

fairth

The word fairth means picture.

garjzla

The word garjzla means light.

istalri

The word istalri means flame.

kveykva

The word kveykva means Lightning.

stenr

Teh word stenr means stone.

vindr

The word vindr means wind.

Energy draining

W reach 7th level, you learn, how everything is connected. You find out, how to make energy flow from one living being to another. You can perform a 10 minute ritual to drain the energy of an unconscious beast. Doing so, you regain a spell slots of your choice, which must have a combined level of half the creatures CR or lower. The beast dies.

Fight with Dragons

When you reach 10th level, dragons begin to recognize you as their ally. You gain resistance to dragons breath attacks.
You have advantage on attack rolls against creatures within melee range of a dragon. Additionally you have advantage on persuasion checks against dragons.

Know you True Name

When you reach 15th, you find out your true name. Knowing your true name makes you sure who you are. You can't be charmed by creatures not knowing your true name.

Frend of Dragons

When you reach 18th level, you learn the ancient draconic word vinr skulblaka for dragon friend. Calling that word in your mind tells the dragons within 10 miles of you, that you need help.
If there is a dragon within 10 miles of you, that is not hostile towards you, it comes to help you. It is not charmed and acts normally but this effect doesn't make it hostile towards you by itself.