Lord Betrayus, whose full name is Betrayus Sneakerus Spheros, serves as the main antagonist of Pac-Man and the Ghostly Adventures. He is the supreme ruler of the Netherworld, a dark dimension populated by ghosts and monsters, and commands a vast army of spectral beings. His backstory reveals that he was not always a ghost; he was once a living citizen of Pac-World. He was a rebellious general who instigated a massive war against Pac-World, driven by a deep-seated ambition and a bitter rivalry with his brother, Stratos Spheros, who is the president of Pac-World. For his crimes, which included leading a revolt and committing terrible acts, Betrayus was stripped of his physical body and banished to the Netherworld as a ghost, along with his allies.

His primary motivation is revenge and a lust for power. He seeks to conquer Pac-World and rule it with an iron fist, finally proving his superiority over his brother and all other Pac-People. A key part of his plan involves obtaining power berries, which are a source of immense energy in Pac-World, believing that controlling them will make him unstoppable. He is also personally resentful of the series protagonist, Pac-Man, who is the last remaining "Yellow One" and the only one with the ability to stop his schemes. Betrayus is frequently shown watching television in his throne room, scheming and reacting to the news of Pac-Man's latest victories.

In terms of personality, Betrayus is arrogant, short-tempered, and flamboyant, with a hammy and often dramatic delivery. He is utterly convinced of his own brilliance, yet his plans are consistently marked by impulsiveness and a lack of foresight, making him a largely incompetent and bumbling villain. He is a coward at heart, preferring to send his ghostly minions to do his dirty work while he remains safely in the Netherworld. When his schemes fail, he is prone to throwing childish tantrums and placing all the blame on his underlings, such as his chief scientist Dr. Buttocks and his loyal servant Butt-ler, rather than accepting his own errors. This behavior highlights his role as a comic foil to the heroes, often serving as the object of ridicule rather than a genuinely terrifying threat.

Despite his comical failures, Betrayus maintains key relationships that drive the plot. His most significant relationship is his rivalry with his brother, Stratos Spheros, which is rooted in a lifetime of feeling overshadowed and disrespected. He is also the primary enemy of Pac-Man, whom he constantly vows to defeat. His control over the Netherworld is maintained through fear and abuse, as he constantly belittles and bullies his ghostly subordinates, including the famous Ghost Gang of Blinky, Pinky, Inky, and Clyde, who secretly work against him. His past includes a personal humiliation when he lost a Pac-Pong championship to Spheria, Pac-Man's aunt, for whom he once had an unrequited crush.

As a ghost, Betrayus possesses a standard set of supernatural abilities. He can fly, become intangible to pass through solid objects, and possess living beings or machinery. He is also known as the Ultimate Fire Ghost, granting him the power to control and manipulate fire, which he can project from his body or his claw-like hands. A unique aspect of his ghostly nature is his effective immortality; because he is already dead, being eaten by Pac-Man does not permanently destroy him. Instead, his physical form will eventually regenerate in the Netherworld, allowing him to return and scheme another day. His appearance is distinct from other ghosts, featuring a white, catfish-like physique with glowing red eyes, sharp fangs, robotic claws, and a spiky mane of white, black, and red hair.