Mortakk

Mortakk was noted as the blackest character in Silurian history in an parallel version of Earth.

His crimes included conducting genetic experiments on both Silurians and Sea Devils. He was later tried and believed to have been executed before the great hibernation. However, his base was located in an abandoned nuclear research centre at Darkmoor and The Doctor along with Benny and the Silurian scientist Thactus of URIC take the TARDIS to confront him.

Mortakk had indeed survived and created a gas with mutagenic properties that forcibly evolved Silurians or Humans to evolve into hybrid creatures containing both reptilian and mammalian qualities. This brought him into conflict against his enemies and Mortakk himself fought the Doctor in a sealed room when the gas was released. However, due to his Gallifreyan biology, he was not affected and Mortakk was killed in the process. (DW: Final Genesis)


 * Its not known whether Mortakk exists within the mainstream Earth.