Fire

Fire was energy produced by rapid oxidation. The earliest splinter of Scaroth showed mankind how to make fire (DW: City of Death) and by roughly 100,000 BC, fire had become a precious commodity, as relatively few humans knew how to recreate it once it was snuffed out; in some tribes this knowledge was held only by a select few. The First Doctor and his companions Ian Chesterton, Barbara Wright and Susan Foreman encountered a tribe looking for this knowledge; Chesterton ultimately showed Za, a tribal leader whose predecessor was unable to give him the secret before dying, how to make fire. (DW: An Unearthly Child)

The Tenth Doctor once commented that fire was "so fun to look at! But bad for the skin!" (IDW: Ground Control)

Incidents involving fire

 * The First Doctor accidentally inspired Nero to start the Great Fire of Rome in 64. (DW: The Romans)
 * The Third Doctor saw an alternate Earth consumed by fire. (DW: Inferno) This memory was used against him by the Keller Machine. (DW: The Mind of Evil)
 * Ky used fire to ward of Mutts. (DW: The Mutants)
 * During the Fourth Doctor's sacrifice by the Deons, fire was used to burn the ropes holding a rock above him. (DW: Meglos)
 * In Victorian era London, Leela savagely attacked the Linktons' teleportation device. It sparked and started a fire. This fire then went on to melt the Linktons present, as they were mostly made of wax. (PHS: The Living Wax)
 * The Great Fire of London started when a Terileptil weapon overloaded in a building on Pudding Lane, London in 1666. Much of the city was burnt, but it proved helpful in clearing the bubonic plague from the city. (DW: The Visitation)
 * The Tenth Doctor used a burning stick to light a funeral pyre for the Master. (DW: Last of the Time Lords)
 * When a future Eleventh Doctor was killed by an astronaut, a funeral pyre was lit for him by Amy Pond, Rory Williams, and River Song. (DW: The Impossible Astronaut)
 * Jack Harkness once encountered a firebird, a creature literally made out of fire. (TW: Immortal Sins)