Gladiolus is a childhood friend of Noctis and Ignis, the eldest son of Clarus Amicitia and older brother to Iris Amicitia. As a member of the Crownsguard (members of House Amicitia are the traditional leaders of Crownsguard), Gladiolus acts as the shield of Noctis, like his father has been to King Regis. He has known Noctis since childhood and considers him a brother. Gladiolus ensures the team does not sway from their goal, and holds Noctis to a high standard, ensuring that he is at his best and sometimes offering brutally honest and blunt advice. He takes great pride in his role as Noctis's sworn shield, and will rush to defend him from harm.
Gladiolus is a tall man with a large build. He wears black leather trousers with a small side chain, and an open black shirt with nothing but a pendant underneath. In the "no jacket" version of his outfit, he wears a black tank top with the Crownsguard's insignia in gray.
He has a small arm sleeve over his left wrist, and wears black shoes with red soles. He has amber eyes, a long scar over his left eye. Gladiolus has a large tattoo of a bird of prey that covers his entire back and extends down his arms. The full tattoo is visible with the Rugged Attire. The tattoo is for male line of the Amicitia, and is the credential of the King's Shield rather than a family crest, the family members getting their tattoo when they become one of the shield. Gladiolus's father Clarus Amicitia has the same tattoo. In his casual attire, his belt buckle also portrays an eagle.
Gladiolus obtains more scars during the game. His long brown hair is shaved along the sides, and he sports a jaw beard. Like all party members, he has skull motifs to his outfit; the buttons on his jacket have skulls on them, his necklace has two golden skulls, and there is a small skull on his belt buckle and on the tag of his trousers' zipper.
Ten years later, the sides of his hair have grown back. His hair is longer, and he keeps it in a small ponytail. The tattoo on his arm has slightly faded, and he wears the Kingsglaive uniform.
I've served as your Shield through thick and thin. No matter what, I've got your back—now and always!
—Gladiolus Amicitia
Gladiolus is a cheerful person, contrasting with his imposing physique. Gladiolus has been a fan of the great outdoors since he was young, and has collected various Coleman camping equipment items. He enjoys fighting, and thus researches techniques and skills.
Gladiolus comes from a family that has always been protectors of the Lucian royal family, and is the only party member with a militaristic background. Not only is he trained to protect Noctis, but he's also his friend. Gladiolus freely expresses his opinions on what's necessary and acts as a pillar in ensuring that the team doesn't sway from their goal. This directness leads him into arguments with Noctis. Gladiolus holds Noctis to a high standard as the heir apparent, and becomes impatient with him if he doesn't think Noctis is trying hard enough. Their confrontations can escalate to a physical level, Gladiolus grabbing Noctis by the shirt to lecture him, and generally acting in a threatening manner. However, he takes great pride as Noctis's sworn shield and instinctively jumps between Noctis and anyone who tries to harm him. Stemming from this, Gladiolus is blunt when it comes to humor. Gladiolus is confident in his abilities, but at times fears he is not strong enough for the position of the future king's shield. He is flirtatious with women, earning Prompto's ire.