Regeneration (Time Lord)

A Time Lord has thirteen lives all told; when at the end of one life, they can regenerate into a new body. This is a property unique to Time Lords/Ladies. There have been suggestions that some were able to extend the number of regenerations; however, the only known cases of this are The Master, under unusual circumstances -- twice by taking over a human (or other non-Time Lord) body, and the third time when he was resurrected and given a new set of regenerations by the Time Lords. This was not, on reflection, a very good idea.