Saint Nerona Imu

Imu has chiefly been shown in a partial devil transformation, revealing a clearly formed nose and mouth, lengthy lashes, dark skin, and pale hair that drapes over the left eye. The sharp, almond-shaped eyes hold red irises ringed by multiple bands. Two curling horns, long black claws, and circuit-like markings adorn the body, including an eye-shaped design on the back of each hand, a jagged line running down the left side, and white dots scattered across the limbs and torso. A cloak bearing two Covenant symbols covers the muscular frame, worn with a furred belt, baggy pants, spiked bracelets, and pointed black shoes; in this form Imu is notably larger than ordinary humans.

For much of the story Imu was kept hidden in silhouette, appearing as a shadowy humanoid with only the eyes visible, crowned by a tall four-spiked headpiece and a robe that trailed far across the ground. While possessing others through their Covenant, Imu could turn the host's eyes to match their own and project a shadowy figure to speak or strike.

Imu is a self-obsessed, pitiless tyrant who regards themselves as a god, though they admit seeing little distinction between a god and a devil. Prizing absolute control above everything, Imu believes all people crave power and views others merely as tools for their goals or as obstacles to the world's "completion." That callousness extends to mass murder: Imu chose the Lulusia Kingdom for the Mother Flame's first test purely because of its location, brushing aside the many lives lost, a request that startled even the Five Elders.

Despite craving total dominion, Imu has long ruled from the shadows and turned their very existence into one of the world's gravest taboos, with anyone who learns of it marked for death. Only in dire moments does Imu act directly, as when the suffering of Mary Geoise pushed them to possess Gunko and later travel to Elbaph in person, enduring a heavy physical toll. Many of Imu's fixations trace back to the Great War, especially the scattering of the Poneglyphs and the part played by Nefertari D. Lili, which Imu calls her "great mistake." Holding fatalistic and inherited-will beliefs, Imu addresses present-day foes by their forebears' names, naming Rocks as "Davy Jones" and Luffy as "Joy Boy."

Usually calm and unflappable, Imu tends to dictate conversations rather than negotiate and rarely shows emotion even in battle, though they favor brutal wounds. Memories of Void Century contemporaries break that composure; Imu screamed in agony on sensing Joy Boy's Haki and later killed Elder Jaygarcia Saturn in a rage for letting Luffy escape. Imu uses the unique self-pronoun "Mu."

As ruler of the Empty Throne, Imu holds unchallenged authority over the entire World Government, commanding the Five Elders, publicly seen as its top authority, and the Knights of God, with the sole right to strip and replace an Elder's title. Many of those subordinates draw their abilities from Imu directly. Their personal combat strength ranks among the world's greatest: while inhabiting Saturn at the God Valley Incident, Imu single-handedly took on Rocks D. Xebec, future Emperors, Roger, and Garp at once, and on Elbaph they shrugged off attacks from Zoro and Sanji, downing each with a single counter.

Imu commands an Ancient Weapon fueled by Vegapunk's Mother Flame, a floating armament that erased the Lulusia Kingdom in seconds. Their body, however, is unsuited to leaving Mary Geoise, leaving them sick and bleeding internally when they do. Imu is also undying and seemingly ageless, regenerating from any wound; Emporio Ivankov has speculated that a former Ope Ope no Mi user granted Imu eternal youth through the fruit's life-restoring surgery, and Imu can pass that immortality on to those bound by Covenant.

Imu carries the Akuma no Mi, letting them become a devil with wings and a piercing tail, and conjure esoteric forces: the Abyss circles for instant travel, the black Omen flames as projectiles, and a book that summons weapons. Through Covenants Imu can grant powers to others while gaining the ability to control or possess them, and can warp foes into mindless immortal demons via Domi Reversi. A user of both Observation Haki and the rare Supreme King Haki, Imu can flatten multiple giants across Elbaph at once. Their favored weapon is a glaive with a zigzagging blade whose pommel reshapes into a cannon, mace, or flail, and they also wield tridents, daggers, firearms, and a saber.