Add is a sentient Mystic Code and an alternate vessel for the Holy Spear Rhongomyniad, crafted to preserve the weapon’s arcane essence. He takes a compact, cube-like shape to obscure the spear’s true nature and reduce its burden on the wielder, serving as Gray’s primary weapon system. Highly talkative and sarcastic, Add frequently offers commentary and displays distinct humor; his speech patterns and mannerisms reflect those of Sir Kay, brother of King Arthur, stemming from Rhongomyniad’s ties to Arthurian legend. In combat, Add transforms into versatile armaments such as a scythe (deliberately avoiding a spear’s appearance), bow, or shield as needed, while also providing observational insights during investigations. Add’s existence is bound to Gray’s destiny, as he was created through her village’s efforts to forge a vessel for Artoria Pendragon’s legacy. As Gray’s appearance gradually shifts to resemble Artoria’s due to wielding Rhongomyniad, Add remains her constant companion, observing and remarking on her struggles. He enforces strict limits on Gray’s access to Rhongomyniad’s latent energy, though emergency protocols can temporarily override these restraints in dire scenarios—prolonged use risks eroding her physical form and sense of self. Within certain contexts, Add is classified as Gray’s Noble Phantasm, reflecting his divine-construct origins and affirming his role as her primary armament. His sentient nature and independent conversational abilities persist throughout.