Finnian, known as Finny, is the gardener at Phantomhive Manor. He was previously imprisoned as test subject "S-012" in a secret laboratory, where injections granted him superhuman strength, speed, endurance, and regenerative abilities. During a raid on the facility, a doctor executed other subjects but hesitated before killing Finnian, enabling him to react violently and escape. Ciel Phantomhive and Sebastian Michaelis later discovered him. Ciel named him "Finnian" after the Celtic hero Fionn mac Cumhaill, famed for speed and strength, securing Finnian's unwavering loyalty. Ciel also gifted him a straw hat to hide the "S-012" brand on his neck. Finnian initially suffered severe trauma from captivity, including claustrophobia and uncontrolled strength that often broke objects. Working outdoors as a gardener helped him manage his fear and find purpose. Within the household, Finnian displays a cheerful, excitable, and sometimes naive personality. His superhuman abilities frequently cause accidental destruction of gardens or property, drawing reprimands from Sebastian for carelessness. Yet he exhibits fierce protectiveness when Ciel is threatened, shifting into a combative state where his experimental powers fully emerge. He shares close camaraderie with fellow servants Mey-Rin and Baldroy, often teaming up with them during crises. Key developments unfold across story arcs. In the Circus Arc, intruders from Noah's Ark Circus attack the manor. Finnian confronts performer Jumbo, surviving a head blow fatal to normal people. Enraged when Jumbo damages his cherished straw hat, Finnian kills him. Later, he battles circus members Peter and Wendy, showcasing durability and combat skills. During the Emerald Witch Arc, Finnian reveals basic German fluency, hinting at a past connection to a German-speaking facility. When Ciel suffers a breakdown, Finnian defies Sebastian to comfort him, showing his loyalty transcends hierarchy. His abilities are further highlighted when he carries witch Sieglinde Sullivan while evading gunfire, demonstrating superhuman speed and agility. Finnian narrates the theatrical production in the OVA "His Butler, Performer," though his role is minimal. Throughout his service, Finnian acknowledges Ciel gave him an identity beyond being an experiment, allowing him to channel destructive capabilities into nurturing plants. His arc centers on gratitude towards Ciel, the ongoing struggle to control his powers, and dedication to protecting the Phantomhive household.