Sebas Tian functions as chief butler and head steward of the Great Tomb of Nazarick, directing domestic operations and managing subordinate staff such as the Pleiades Six Stars combat maids and general manservants. Created by the Supreme Being Touch Me, he originally served within Nazarick's final defense line on the 9th Floor alongside the Pleiades, tasked with delaying invaders to afford guild members preparation time. He presents as an elderly human butler with sharp eagle-like eyes, white hair, a neat beard, and a formal black tuxedo. His true nature is that of a Dragonoid heteromorphic being, a guise adopted to blend into human settlements during reconnaissance missions.

Inheriting his creator's sense of justice, Sebas operates by the principle "those who do not save the weak cannot call themselves strong," distinguishing him from most Nazarick inhabitants who deem humans inferior. He demonstrates compassion through actions like rescuing Tuareninya Veyron from a brothel and nursing her back to health. Conversely, he shows no mercy to those he judges morally corrupt, such as the Eight Fingers criminal organization, and prioritizes Nazarick's interests above all. This duality sparks internal conflict, especially when his actions risk seeming disloyal, exemplified by the Tuare incident which aroused suspicions of treachery in Demiurge and other guardians. His loyalty to Touch Me exceeds even his devotion to Ainz Ooal Gown, and his opposing worldview fuels tension with Demiurge, whose creator rivaled Touch Me.

An unarmed combat specialist ranked among Nazarick's four strongest warriors, Sebas can overpower Floor Guardians Albedo and Cocytus in his Dragonoid form. His physical prowess includes intercepting poison daggers mid-flight, tearing off steel doors, and delivering strikes that rupture internal organs or launch armored opponents lethally. As a Monk and Ki Master utilizing Ki, his abilities include *Iron Skin* for enhanced defense, *Healing* for physical wounds (ineffective against diseases or poisons), the *Palm of the Puppeteer* to render targets unconscious and compliant via touch, and *Ki-enhanced strikes* sharpening his hands beyond bladed weapons. He also possesses sensory abilities like life-form detection through Ki Sense and opponent strength assessment.

Across official media, his story involves gathering intelligence in Re-Estize and E-Rantel, frequenting adventurer and mage guilds to compile reports. His rescue of Tuare triggers a confrontation with the Six Arms, whom he eliminates effortlessly, earning the moniker "Iron Butler." Following a loyalty test where he agrees to kill Tuare if commanded, she is integrated into Nazarick as a maid under his and Pestonya Shortcake Wanko's tutelage. In the *Mass for the Dead* spin-off, he coordinates the Pleiades during crisis response, emphasizing teamwork and hospitality protocols while mentoring Lupusregina Beta in service etiquette. After the Sorcerer Kingdom's establishment, he relocates to E-Rantel as head steward, losing command over the Pleiades but continuing to manage Tuare's training.

Notable differences exist between adaptations: the web novel depicts him rescuing eight women and maintaining a harem-like arrangement, while the light novels focus solely on Tuare. Non-canon game scenarios portray his personality as more easygoing.