As the king of Lucis, he is referred to as King Regis or Regis Lucis Caelum CXIII. He uses the Ring of the Lucii to channel the power of Insomnia's Crystal to maintain the Wall, but this gradually drains his life-force. Regis thus feels ambivalent his son, Noctis Lucis Caelum, would have the same fate befall him.
Regis is a rapidly aging man with gray hair and green eyes. In his youth, his hair was black. On most occasions, Regis wears a black suit with thin, white stripes, and a black cape. He wears a gold brace on his right knee, and black shoes. Regis uses a cane to walk, and a silver, hornlike crown on the right side of his head, held behind his ear. The crown may be intended to allude to Bahamut who has curved horns on his helmet in his true appearance and on the Kingsglaive emblem. The golden ornaments on his cane and braces also have wing motifs, like the royal arms do.
As a Lucii, Regis retains most of his appearance, but wears a suit of armor, and a helmet that covers his head and face.
A king pushes onward always, accepting the consequences and never looking back.
—King Regis
Regis believes those of his royal bloodline are strong of heart and will, although he is deeply saddened by the fate that awaits Noctis. His son's safety is his first priority. He helps Noctis grow and shows him what it means to be a king. Out of everyone he meets, Regis has the greatest impact on Noctis's life. Regis wants Noctis to find his own path in life, and as such, asks Ignis, Gladiolus, and Prompto to not guide Noctis, but rather stand by his side as he finds his own way.
Regis uses the Ring of the Lucii to channel the power of the Crystal, and can use magic. Through the ring he creates and maintains the Wall, a magical barrier that shields the Crown City from outsiders. This gradually drains Regis's life-force, and thus he is unable to command the Old Wall. He is a skilled swordsman capable of summoning weapons from thin air, and can use Armiger. His personal royal arm is the Sword of the Father. He uses the Ring of the Lucii to cast powerful spells, such as Thunder and Protect. He chooses to lend his powers to the Kingsglaive who thus protect the kingdom as an extension of Regis himself.