The Charon were a race retroactively destroyed by the Time Lords billions of years ago in a time war. The Charons had the ability to warp the fabric of the universe. The Time Lords erased the Charons before they existed as they feared that all other life in the Universe could not co-exist alongside them.
One individual Charon somehow survived the death of its people and constructed a pocket universe, with its own physical laws, and populated it with many different forms of life, including Humans and Sloathes.
Thousands of years later, the Charon manipulated the inhabitants of its universe to bring the Eyes of the Schirron to it, which would trigger its rebirth cycle, but also destroy its universe and everything in it. The Doctor confronted the Charon and learned that, after being alone for so long, it wanted to die. The Doctor sadly granted its wish. (NA: Sky Pirates!)