Originally a human salaryman named Satoru Suzuki from 2138 Japan, Momonga co-founded the YGGDRASIL guild Nine's Own Goal. This guild, later renamed Ainz Ooal Gown, consisted solely of heteromorphic players who embraced villainous roles after facing in-game discrimination. As guildmaster, Momonga led the conquest of the Great Tomb of Nazarick, turning it into a fortress defended by custom NPCs and World Items. He remained logged in as his lich avatar "Momonga" during YGGDRASIL's shutdown, awakening in a New World where Nazarick became physically real and NPCs gained sentience. He eventually adopts the name Ainz Ooal Gown publicly. His skeletal undead form lacks flesh, features dark red luminous points in its eye sockets, a floating crimson orb within the ribcage, and a dark halo behind the skull. He typically wears ornate black academic robes trimmed in gold and purple. As the adventurer "Momon," he dons black plate armor with purple-gold markings and a red cape, wielding twin swords. Later, as Sorcerer King, his attire becomes white-and-gold ceremonial robes with rainbow-accented gauntlets. His undead body suppresses human emotions, resulting in calculated pragmatism. He prioritizes Nazarick's safety and legacy above all, using strategic deception like feigning omniscience to maintain authority over devoted NPCs such as Albedo and Demiurge. Loyal to memories of his guildmates, he views New World inhabitants instrumentally: aiding humans like Enri Emmot or Gazef Stronoff when nostalgic or beneficial, yet enacting brutal experiments, mass killings like annihilating the Re-Estize Kingdom, and undead conversions to expand influence. He avoids romantic entanglements with NPCs out of respect for their creators. Key developments include saving Carne Village from knights (adopting "Ainz Ooal Gown" as his public name), infiltrating E-Rantel as Momon to gather intelligence, defeating the mind-controlled Shalltear Bloodfallen using guildmates' relics, establishing the Sorcerer Kingdom, and orchestrating the Holy Kingdom's crisis via the demon emperor "Jaldabaoth" (Demiurge in disguise). His abilities derive from adapted YGGDRASIL mechanics: immunities to mind effects, instant death, and elemental damage (excluding holy/fire vulnerabilities); command of over 700 spells emphasizing necromancy and instant-death magic; access to Super-Tier spells like "Iä Shub-Niggurath" summoning Dark Young; and daily undead creation such as Death Knights. He obsessively hoards items, including World-Class relics. His journey shifts from cautious exploration to active world domination, driven by the desire to reunite with lost guildmates and immortalize Ainz Ooal Gown as an eternal legend. His dual identities—benevolent ruler to allies, merciless conqueror to foes—underscore his complex allegiance to Nazarick above moral boundaries.