Serpent

From Tardis Wiki, the free Doctor Who reference
Serpent
The serpent-like form of the Mara. (TV: Kinda)

The Mara was described as a serpent. (TV: Snakedance) Before peace was signed, the Great Houses created artificial serpents which they sent to the Osirian Court to devour Ra, (AUDIO: Coming to Dust) of which the greatest was Apep, until the Osirians managed to reprogramm him. (PROSE: Going Once, Going Twice)

Kara Seddle called Davros a serpent in the paradise of her company when hiring Orcini, a Knight of the Grand Order of Oberon, to kill him and his Necros Daleks. (TV: Revelation of the Daleks)