Ashad

A partially Cyber-converted human, originally known as Ashad, came to be known as the Lone Cyberman when he re-lit the flame of a lost Cyber-Empire. Though at first he was rejected, when offering himself up for conversion, Ashad later played a key role in the re-ascension of the Cybermen, following their near-annihilation in the Cyber-Wars.

Though he maintained much of his human appearance, as well as temperament, Ashad despised his own kind throughout. Loyal to the cause he believed in, and filled with hatred, the Lone Cyberman sought to restore the Empire to its former glory, and then to extinguish all life, beyond the race he revered.

Origin
Originally human, (TV: Ascension of the Cybermen) Ashad had multiple children before undergoing cyber-conversion, transforming him into a Cyberman. He did not have an emotional inhibitor, stating he "[did] not need to be stabilised". As he recalled to the Thirteenth Doctor and Mary Shelley, his children joined the resistance and so he slit their throats. (TV: The Haunting of Villa Diodati)

Ashad offered himself up to join the ranks of the Cybermen, but they rejected him. Regarding himself as a "believer", however, he stayed committed to the cause. After the Cyber-Army was all but lost, he took it upon himself to revive the Empire, as their champion. (TV: Ascension of the Cybermen)

Forewarning
Captain Jack Harkness once tried to contact the Doctor to warn him and "beware of the Lone Cyberman" and to not give it what it wants. However, he got hold of Ryan Sinclair, Yasmin Khan and Graham O'Brien instead, initially believing them to be the new Doctor. When he was told that he was she, he told them to warn her instead and tell her about a fallen empire. (TV: Fugitive of the Judoon)

Searching for the Cyberium
Ashad travelled back in time to 1816 to attempt to extract the Cyberium, the database of Cyberman history, from Percy Shelley. The Thirteenth Doctor absorbed it herself, knowing Shelley's death would alter the future. However when Ashad threatened to tear reality by summoning his ship, she relinquished the Cyberium to him, knowingly ignoring Captain Jack's warning but deciding she would rather confront the Cybermen in the future than change the course of history by having the Earth destroyed in 1816. After taking the Cyberium, Ashad disappeared. (TV: The Haunting of Villa Diodati)

Personality
Due to his lack of an emotional inhibitor, Ashad was able to express and understand emotions and even tended towards anger issues. Despite this, he lacked mercy or remorse, being completely loyal to the Cybermen and revealing he killed his own children for joining the resistance. He also knew how to manipulate emotions, as shown when he taunted Mary Shelley about sparing her son not out of pity, but because he was unsuitable for conversion, and when he blackmailed the Doctor into handing over the Cyberium or he'd tear reality by summoning the ship. (TV: The Haunting of Villa Diodati)