Greed manifests as Father's homunculus, the physical incarnation of avarice purged from Father's being. His Ouroboros tattoo marks the back of his left hand. Originally, he appears as a tall, muscular man with short, spiky black hair slicked back, purple eyes featuring cat-like pupils, sharp teeth, and distinctive red lines across his torso. His attire typically consists of a black leather jacket with a fur collar, a skintight shirt, leather pants, pointed shoes, wrist belts, and occasionally sunglasses. Activating his "Ultimate Shield" ability transforms his entire body into dark blue, diamond-hard carbon armor with razor-sharp claws, red sclera, white irises, and demonic features, achieved by rearranging skin carbon atoms into near-impenetrable graphene shielding.

After defeat by Wrath (King Bradley), Father forcibly dissolves and reabsorbs Greed. He later reemerges reborn through a Philosopher's Stone implanted into Prince Ling Yao's body. This merged "Greedling" state retains Ling's form but displays altered features: slit-pupiled purple eyes, paler skin, and the visible Ouroboros tattoo on the left hand. Control over the shared body shifts between personalities, visually signaled by hairstyle - Greed's covering his right eye versus Ling's left. This coexistence grants Greed access to Ling's martial arts expertise and chi-sensing abilities, compensating for his previous combat limitations.

As a homunculus, Greed possesses inherent traits: agelessness, Philosopher's Stone-powered rapid regeneration, toxin immunity, and physical capabilities exceeding human limits. His Ultimate Shield allows selective or full-body carbon hardening for defense, with claws capable of slicing metal and stone. The shield's vulnerabilities include alchemical transmutation of its carbon into brittle graphite and an inability to regenerate while activated. His personality embodies avarice, craving money, power, status, women, and eternal life. He claims never to lie (though he does so once to save Ling) and refuses to harm women or children. While viewing humans as weak, he lacks the hatred typical of other homunculi and exhibits charisma that attracts loyal followers, whom he initially considers "possessions."

Greed's history includes rebellion against Father over a century prior to the main events, leading him to form a Dublith gang of chimeras. His first incarnation ends when Wrath executes his subordinates and captures him, resulting in reabsorption. Reborn without memories, he initially serves Father until regaining his past after killing former follower Bido. This reignites his grudge against Wrath and prompts an alliance with Ling, who helps him realize his true desire is genuine friendship, not material wealth. Interactions with Edward Elric, shifting from battle to alliance against Father, further evolve his worldview to respect human tenacity and the value of bonds. His journey culminates in sacrifice during the battle with Father; exploiting his carbon manipulation from within Father's body, he weakens Father's form to enable Edward's final attack, accepting death as he states his friends have given him "everything."