CyberMaster

The CyberMasters were a race of Cybermen created by from the corpses of the Time Lords who had been on Gallifrey when he destroyed the Capitol, claiming them all to have been "born" from the Doctor. (TV: The Timeless Children)

Characteristics
The CyberMasters possessed Cyber-bodies very similar to those of the Cyber-Warriors that Ashad reawakened in the aftermath of the Cyber-Wars of the Cyberium, though they possessed several notable differences.

The Cyber-helmets of CyberMasters had large, silver Time Lord headdresses, with Gallifreyan symbols on the sides and the outer layer of their faceplates, in place of a pair of side handles. The CyberMasters' faceplates also featured "tear-drop" eye-pods that angled vertically, rather than diagonally, and their mouth slits were grated frowns. In addition, each CyberMaster wore long, blue robes that draped their backs. (TV: The Timeless Children) The voices of CyberMasters were highly reminiscent of the voices of the early Cybermen of Cybus Industries. (TV: Rise of the Cybermen, The Age of Steel) The CyberMasters possessed cyber wrist blasters identical to those of the Cyber-Warriors they were based upon; several dozen blasts from these wrist blasters could mortally injure a human, with the injuries sustained leading to death within a second.

The most striking characteristic of the CyberMasters was their ability to regenerate; converted these CyberMasters from the corpses of Time Lords and genetically spliced the Time Lords' regeneration abilities into the CyberMasters. This effectively gave the CyberMasters an advanced self-repair system, allowing them to regenerate and recover from otherwise-fatal damage. The Master proclaimed that this made the CyberMasters "invincible", and demonstrated to the Thirteenth Doctor the CyberMasters' regenerative powers by having one CyberMaster shoot another CyberMaster with its Cyber wrist blaster; the former CyberMaster was temporarily terminated, but quickly regenerated and fully restored itself. However, as they contained organic components, the CyberMasters were still vulnerable to the death particle, even after it had been shrunk by the Master's Tissue Compression Eliminator.

Anomalously, although the CyberMasters, being a Cyber-subspecies, were programmed to be emotionless, they would not immediately obey an order if it would result in damage to a fellow CyberMaster; indeed, when the Master demonstrated the CyberMasters' regenerative capabilities to the Doctor, the CyberMaster he ordered to shoot at a fellow CyberMaster was initially reluctant to do so, until the Master angrily ordered it to comply. (TV: The Timeless Children)

History
In response to discovering the lie of the Timeless Child which the Time Lords had kept hidden, returned to Gallifrey and killed them all but made sure to preserve their bodies, keeping them "just cold enough" in the event they could be of use to him. That point came when a Cybercarrier from the aftermath of the Cyber-Wars passed through the Boundary to Gallifrey. Commandeering the resources of the Cybermen, the Master engineered a new race which he named the CyberMasters, Time Lord organics with the ability to regenerate and self-repair in Cyberarmour, effectively making them invincible.

Under his command, the CyberMasters were presented by the Master to the Thirteenth Doctor; the Master claimed that CyberMasters were "born" from the Doctor, who was originally the Timeless Child. Deeming that the CyberMasters could not be allowed to leave Gallifrey, the Doctor considered detonating the death particle, which had the power to obliterate all organic life on a planet, to stop them, but her place was taken by Ko Sharmus. On the Master's order, the CyberMasters repeatedly shot Ko Sharmus, who nonetheless detonated the death particle, destroying the Capitol. The CyberMasters were last heard from when the Master ordered them to follow him out through another exit way. (TV: The Timeless Children)