Escanor, second prince of Castellio, manifested uncontrollable power called Sunshine during childhood. This power accidentally broke his older brother Daymond's arm, leading to his disownment. His parents mobilized the kingdom's forces to execute him. A woman named Rosa saved him, hiding him in a barrel set adrift at sea. Throughout exile, he faced ostracization and was labeled a monster despite attempts to help others. A later return revealed Castellio in ruins and Rosa missing.

Years later, while eliminating a rampaging monster in Liones, he was mistaken for the instigator. Holy Knights, including Great Holy Knight Zaratras, intervened and were gravely injured. Captured and accused of terrorism, disrespect to the king, and injuring knights, he was sentenced to death as the Sin of Pride. Meliodas intervened, recruiting him as the final member of the Seven Deadly Sins. Initial fear of the group subsided when they welcomed him, partly due to Merlin's resemblance to Rosa.

Escanor's physiology and personality fluctuated dramatically with the sun's cycle. At night, he appeared meek, frail, and submissive, exhibiting skittishness and unfailing politeness. Daylight triggered a transformation: his physique became muscular and imposing, while his personality shifted to boastful, domineering, and judgmental toward those he deemed sinful. Both personas retained deep affection for Merlin, fondness for poetry, and loyalty to comrades. His pride granted immunity to certain demonic commandments, as he viewed hatred as beneath him, feeling only pity for opponents.

Sunshine, originating as the Grace of the Archangel Mael, caused his strength to peak at noon—reaching a state called "The One" where he became invincible for one minute—and waned until nightfall. Intense heat radiated from him, capable of vaporizing lakes and burning souls. He wielded the Divine Axe Rhitta, storing excess solar energy for later use. Techniques included "Cruel Sun," a miniature sun projectile, and "Divine Sword Escanor," a hand-swipe energy slash. Prolonged use of Sunshine drained his life force, a fact he acknowledged but disregarded to protect others.

Key battles demonstrated his resolve. He defeated Commandments Galand and Melascula at his bar, critically injured Estarossa despite "Full Counter" magic, and shielded allies without powers against an Indura spore, sustaining severe injuries through willpower alone. When gravely injured by the Original Demon, he pleaded with Mael to reclaim Sunshine to aid his comrades. After Mael returned the Grace with a warning of its fatal toll, Escanor accepted it without hesitation.

His love for Merlin remained central, as she was the first to show interest in him without fear. Though never confessing fully, he prioritized her safety and viewed her as his guiding light. During the final battle against the Demon King, he activated "The One: Ultimate," surpassing his limits to deliver a decisive blow. This act irreparably damaged his body, leading to his death. Despite initial intentions to sacrifice himself alone, his comrades insisted on fighting alongside him, prompting a shift in his prideful daytime persona: he valued his life more deeply and embraced teamwork. His final moments included a poetic declaration to Merlin.

Escanor's journey encompassed overcoming isolation, reconciling dual identities, and demonstrating that true strength lies in protecting others—even at the ultimate cost. His character arc concluded with a synthesis of pride and humility.