Dragon

Dragons were creatures from Earth myths and legends, resembling giant lizards.

The Doctor encountered a fire-breathing dragon in the forest outside the Pied Piper's castle, but drove it off with a fire extinguisher. (TVC: Challenge of the Piper)

Senator Alcott's fear of the Chinese manifested itself as a Chinese dragon. (DW: The Mind of Evil)

Dragons were one of the life-forms found on Avalon. (MA: The Sorcerer's Apprentice)

The dragon of Iceworld was a biomechanoid assigned to keep the Dragonfire away from Kane. (DW: Dragonfire)

Dragons also existed in the dreamrealm inhabited by Avalon. The Fair Folk used them to harass infantry and prevent UNIT's domination of the air through the use of fighters. The Doctor rode one deep into Fair Folk occupied territory in order to attempt to forge a ceasefire (EDA: The Shadows of Avalon)