The First was the very first sentient lifeform in the universe. She saw herself as the mother of all living things. She slept for billions of years, waking to find her children fighting, causing wars and sadness. This caused her to create a Reality Virus, to wipe out all creation and start again.
- You may be looking for the First Doctor.
The Thirteenth Doctor and her companion stopped her by sealing her in a time loop. (GAME: The Edge of Time [+]Loading...["The Edge of Time (video game)"])
After one of her defeats in the time loop, the First's virus was re-purposed by the Cybermen of the CyberReaper. Fragments of the First were repurposed for their energy at the centre of Reality Virus transmitters. (GAME: The Edge of Reality [+]Loading...["The Edge of Reality (video game)"])