Time Lords

They are an ancient civilisation of a humanoid species. They were the oligarchic rulers of the planet Gallifrey,

The Time Lords had rewarded The Doctor with extra regenerations for ending the Last Great Time War and saving Gallifrey. Thus allowing The 12th Doctor to exist.

Time Lords have been said to only be able to regenerate 12 times. But it's really limited by the politicians of Gallifrey.

Each hemisphere of a Time Lords' brain controls that half of their body, as opposed to how each hemisphere of a human's brain controls the opposite side.