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.

After intending to destroy all organic life in the universe, Ashad was killed by with the Tissue Compression Eliminator in order to gain access to the Cyberium while the Doctor and her companions blew up Ashad's Cybercarrier and its army of Cybermen, foiling his plans. His remains and death particle was subsequently used by Ko Sharmus to destroy the CyberMasters. (TV: The Timeless Children)

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 only to be "denied" as his upgrade began. Though initially keeping to the shadows out of shame, Ashad stayed committed to the cause and became convinced that he was chosen to ascend the Cyber-race. 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 her to "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)

Restoring the Cybermen
After returning to his own time, Ashad travelled to a refugee planet in a cyberfighter along with two Cyberguards. Upon arrival, he unleashed a swarm of Cyberdrones to destroy the anti-Cyberman defences before he and his guards arrived, managing to prevent all the humans from escaping the planet. Patrolling for the remaining humans and the Doctor, Ashad was confronted by Ethan who claimed to be the only human left and surrendered. Seeing through the ruse, Ashad executed Fuskle and allowed Ethan to live so that he might tell the other species of the universe of the Cybermen's return before he fell victim to an explosive thrown by the Doctor. By the time he recovered, the Doctor had stolen one of his cyberfighters.

Hacking into the craft's communication system, Ashad spoke to the Doctor, unimpressed by her previous victories over the Cybermen, and swore to bring about "the death of everything." Tracking the human craft, Ashad and the Cyberguards arrived at a deserted Cybercarrier. Finding hundreds of thousands of dormant Cyber-Warriors, Ashad removed their organic components before he led some of his army to the carrier's bridge to retake the ship from the humans. (TV: Ascension of the Cybermen)

Alliance with the Master
After Ashad reached the Planet of the Boundary, he realised that humans were aboard the Cybercarrier, though they were able to evade his search by hiding in Cyberarmour. Ashad was subsequently contacted by who offered him an alliance and the planet of Gallifrey. Accepting, Ashad took his ship to Gallifrey through the Boundary, though he left behind death squads to kill the humans still on the planet's surface.

In the Matrix chamber, Ashad met with the Master, though he was alarmed to see the Doctor in a paralysis field. The Master reassured Ashad who explained that his goal was to upgrade the Cybermen to become a purely robotic race before using the death particle created for him by the Cyberium to wipe out all life in the universe. Disgusted by the idea of purely robotic creatures, the Master instead suggested using the Cybercarrier's cyber conversion chambers to transform the deceased Time Lords into Cybermen, an idea that Ashad found appealing.

As the Master and Ashad examined the chambers aboard the carrier, the Master questioned Ashad about the Cyberium and attempted to get it to leave Ashad in favour of him. Ashad furiously told the Master that the Cyberium would never leave him as long as Ashad was still alive. In response, the Master used his Tissue Compression Eliminator to shrink the Lone Cyberman, killing him and releasing the Cyberium. (TV: The Timeless Children)

Post-mortem
The Master, though dismayed that Ashad's death didn't detonate the death particle, was able to convince the Cyberium to take him as its new host and left Ashad's shrunken remains on the floor of the carrier.

Ashad's shrunken body was found by the Doctor as she and her companions destroyed the Cybercarrier and the Cyber-Army aboard it, foiling Ashad's plan to rekindle the Cyber-Empire. Contacted by the Master who had created an army of CyberMasters instead, the Doctor attached Ashad to an explosive in order to sacrifice herself to detonate the death particle and end the Master and his army. However, Ko Sharmus decided to sacrifice himself instead to make up for causing the problem in the first place by sending the Cyberium somewhere that Ashad could eventually find it. In his last moments, Ko Sharmus detonated the bomb, obliterating Ashad's remains and detonating the death particle which wiped out all organic life on Gallifrey, the Master and his army presumably included. (TV: The Timeless Children)

The Doctor also used memories of Ashad and many, many other memories to overload the Matrix on Gallifrey. (TV: The Timeless Children)

After breaking the Doctor out of prison, Jack asked if her friends had given her his message about the Lone Cyberman. Jack was dismayed to learn that the Doctor had given Ashad the Cyberium but she reassured him that she had "fixed it... eventually. Just about. Sort of." (TV: Revolution of the Daleks)

Personality
Due to his lack of an emotional inhibitor, Ashad was able to express and understand emotions and even tended towards anger. 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)

Consumed by self-loathing, Ashad hated his existence as an organic lifeform to the point of seeking out the Cybermen as a means to correct this. Upon receiving the Cyberium, Ashad sought to create a purely mechanised universe first by removing the organic components from the Cyber-Warriors before planning to unleash the death particle and eradicate all organic life from the universe. (TV: Ascension of the Cybermen, The Timeless Children)

Appearance
Having undergone a partial cyber-conversion, Ashad's human body was housed in an incomplete, weathered Cyber-suit resembling those associated with the Cyberiad, (TV: Nightmare in Silver) but with a left arm resembling those of both the planet Mondas and the Mondasian colony ship's first Cybermen, (TV: The Tenth Planet, World Enough and Time, The Doctor Falls) lower legs matching the Cybus-style model assocaited with the Cyber Legions, (TV: Rise of the Cybermen, A Good Man Goes to War) and a unique Cyber-helmet with an incomplete faceplate that exposed the left side of his face. He wielded a functional Cyber wrist blaster, although its energy could be drained by time hopping.

Similar to the converted Alistair Gordon Lethbridge-Stewart, Ashad's side handles were mostly silver but with black corners.

Most notably, Ashad lacked an emotional inhibitor. Being a willing recruit to the Cyber-Empire, he mostly retained control of himself, claiming to the Thirteenth Doctor that he did not need to be stabilised, though he was prone to emotional outbursts. (TV: The Haunting of Villa Diodati, Ascension of the Cybermen)

Behind the scenes

 * Ashad's Cyber-body being a combination of several Cyberman variants evokes the monster in Mary Shelley's Frankenstein.
 * According to NOTVALID: Know Your Enemy, a TARDIS data extract suggested that Ashad had a supercomputer fused to his cerebral cortex.