Cyber Converted Timelords
The Timeless Children
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The CyberMasters were Cyber-converted Time Lords created by The Master from the corpses of all those who had been on Gallifrey when he destroyed the Capitol.
The CyberMasters externally resembled the Cyber-Warriors of the Cyber-Wars, though they had the ornate neckpieces of the Time Lords. As such, they sported Cyber wrist blasters, which were capable of killing humanoids and even other Cybermen. Being Time Lords, however, they retained the ability to regenerate, which made them effectively invincible. (The Timeless Children)
The CyberMasters were apparently destroyed when Ko Sharmus detonated the death particle, obliterating all organic life on Gallifrey. (The Timeless Children)