Merlin, the Boar’s Sin of Gluttony, hails from Belialuin, a neutral city of wizards, where her childhood was marked by cruel experiments sanctioned by her father, the chief sage, under the pretense of unlocking ultimate magic. Emotionally abandoned, she fled and crossed paths with Meliodas, who rescued her from hunters. This encounter ignited an enduring, unreciprocated love, compelling her to halt her aging at thirty and adopt a mature form to attract him. Though Meliodas later chose Elizabeth, Merlin cultivated a sisterly bond with her rival and maintained unwavering loyalty to Meliodas.

A prodigious mage obsessed with knowledge, Merlin suspended her aging to pursue infinite learning. Her discovery of Chaos—a primordial force imprisoned by the Demon King and Supreme Deity—fueled her quest to revive it, envisioning its boundless power as the ultimate answer to her intellectual craving. By tricking both deities into bestowing blessings, she triggered Belialuin’s annihilation, emerging as its lone survivor.

In the Holy War, Merlin collaborated with Meliodas to assemble the Seven Deadly Sins, recruiting figures like Gowther and Escanor. She orchestrated the sealing of the Demon King and Supreme Deity via the Coffin of Eternal Darkness, though her original scheme to resurrect Chaos demanded one deity’s eradication. Her tactical brilliance and composure proved vital in pivotal moments, from neutralizing Galand’s menace to stalling Meliodas’ metamorphosis into the Demon King.

Merlin transitioned into a mentor for Arthur Pendragon, steering him to wield Chaos’ might. After the war, she assisted in rebuilding Camelot before disappearing without trace sixteen years later. Her dynamic with Escanor unveiled unexpected tenderness: she treated him gently despite his volatile power, preserving facial burns from his sacrificial demise as a poignant reminder.

Her appearance shifts between a youthful guise—exposed when magic backfired—and an adult form marked by purplish-black hair, beauty marks, and magically altered, revealing attire. Post-Escanor’s death, she retained the burns as a tribute.

Driven by insatiable curiosity, Merlin dissected both allies and foes, analyzing Escanor’s power surges and Grayroad’s Commandment. Though typically composed, she revealed fragility during crises—Arthur’s near-fatal injury, Meliodas’ regression. Her layered motives, blending loyalty, ambition, and an unquenchable thirst for understanding, solidified her legacy as Britannia’s preeminent sorceress.