This is Gilgamesh: a living weapon, engineered by Nexus during the third great Meister war as a tool of destruction.
He stands approximately 10 feet tall and is the Lord of the Axer class. 
Scars ravaging his body from countless battles, Gilgamesh is infused with several armour implants as a form of defence and a means for his superiors to control the giant beast.

During the final days of the third Meister war, Gilgamesh was rescued and set free from control by Vaan.
As a result, Gilgamesh returned to his naturally docile state and exiled himself, living a secluded life in the frozen tundra of Heaven's peak, among the Triffeca islands.

Not much is known about Gilgamesh's personality as he rarely speaks. He has very little trust in other people as he has been engineered as a living weapons and used as a tool much of his life.
Gilgamesh loves nature, animals and solitude. 

Powers & Abilities:
Gilgamesh wields the Grail known as "Goliath", a giant axe nearly twice the size of an average human. 
Because of his overwhelming raw power, he lives in a constant state of an "Overdrive Plus"; simply unable to reduce his power.