The Cinder

The Cinder, also known as the Phoenix, was an alien creature who was known to exist on Earth from the 12th century B.C. until 1814.

Biology
The creature hatched from an egg, and took the form of a bird made of living flame; in this form the creature was known as the Phoenix. The Phoenix survived by absorbing every last spark of heat from everything around it; if allowed to, it would absorb all the heat from the entire world and kill everything else on the planet. The creature was able to be reborn from the smallest remaining Cinder of its flame. The Cinder, which retained limited memories of its former life as the Phoenix, which would slowly absorb enough heat to regenerate into its egg form, go through its embryonic stage within the egg, hatch as a Phoenix, and begin its life cycle anew.

From within its egg form, the creature was able to telepathically influence humans around it in order to ensure its own survival.

Timeline
In early history, the Cinder existed as a sentient spark, kept faintly alive in an oil lamp by Vicki Pallister as she lived out her life in ancient Carthage. Eventually, the spark was able to transmogrify into the form of an egg. This egg eventually came into the possession of the showman Captain McClavity, who exhibited it at the River Thames frost fair in 1814.

At the fair the creature brought about its own hatching, whereupon it was born as the Phoenix. The First Doctor, his companions Vicki Pallister and Steven Taylor, and local novelist Jane Austen were able to defeat the creature by removing its source of heat, but as Vicki had unknowingly absorbed its final spark as she looked into its flames. In this way, the creature survived undetected.

Much earlier in Earth's history but later in Vicki's personal timeline, she had left the Doctor's TARDIS to live in ancient Troy with the Trojan Troilus. Feeling trapped in a time in which she didn't truly belong and missing the Doctor and her life aboard the TARDIS, Vicki wept for her loss, and found the single spark of the Cinder among her tears. Vicki decided to keep the creature alive in an oil lamp, hidden in a cold, damp crypt beneath a temple in Carthage. There she occasionally visited and talked to the Cinder, having finally found someone with whom she could discuss her adventures with the Doctor.

Vicki knew that one day after her time had passed, the Cinder would eventually reform into its egg and encounter her younger self in 1814. Vicki regretted that she could not alter events to save the people the Phoenix had killed, but she took solace in the knowledge that it would harm nobody else as it was eternally trapped in the same looped sequence of events. (CC: ''Frostfire)

Behind the scenes

 * The Cinder/the Phoenix is based upon the legendary Phoenix.
 * In Frostfire the Cinder serves as the individual to whom the main character relates the story, in the manner of most of The Companion Chronicles.
 * The creature's life cycle is an example of a predestination paradox; the creature is defeated in 1814, its surviving form is taken to Ancient Troy, and that form will eventually grow into the creature defeated in 1814.