Hatchling project

During the War in Heaven, the High Council had several hatchling projects which involved the creation of clones of renegade Time Lords such as the Master and the Rani. Father Kreiner possessed the decapitated heads of both the Master and the Rani and suspected at least one to not be the original but a hatchling. (PROSE: Interference - Book One)

By one account, (PROSE: The Dark Path) who fought the Eighth Doctor (TV: Doctor Who) was an "ersatz" copy. (PROSE: The Dark Path)