I noticed that in 'The Timeless Children' they said that Tecteun spliced the regeneration ability into the Timelords with a 12 regeneration limit. That"s fine, but what of Tecteun her/himself? She should have unlimited regenerations just like the Doctor, and therefor may still be out there.
That said, could Tecteun be the Master? The Master, like the Doctor, had his memory's wiped and was placed with the Doctor as a child. This would explain the close connection between the two. We also saw the Tecteun got a bit dark when trying to discover the secret to regeneration, so he/she could be on the darker side, just like the Master. Of course, this does not explain the Master running out of lives in Tom Bakers era. There could be a reason for that, the Master, for all he knew only had 13 lives, and maybe botched up something with his that regeneration. We do see the Master always survive though, maybe Tecteun had some more special abilities obtained over the centuries, This may also explain how Missy could regenerate to Darwan's Master, etc..
The episode is called 'The Timeless Children' (plural!) so it could be describing the Doctor and the Master. Who knows?
That said, could Tecteun be the Master? The Master, like the Doctor, had his memory's wiped and was placed with the Doctor as a child. This would explain the close connection between the two. We also saw the Tecteun got a bit dark when trying to discover the secret to regeneration, so he/she could be on the darker side, just like the Master. Of course, this does not explain the Master running out of lives in Tom Bakers era. There could be a reason for that, the Master, for all he knew only had 13 lives, and maybe botched up something with his that regeneration. We do see the Master always survive though, maybe Tecteun had some more special abilities obtained over the centuries, This may also explain how Missy could regenerate to Darwan's Master, etc..
The episode is called 'The Timeless Children' (plural!) so it could be describing the Doctor and the Master. Who knows?