Jalnik

Jalnik was a 40th century human scientist.

Due to his time experiments, he unleashed the Pantophagen on Earth. In this alternate timeline, the planet was nearly annihilated. He went back to 1977 to prepare the way for the survivors to escape.

However, some Pantophagen DNA combined with his and resulted in him becoming a Pantophagen-human hybrid. The Fourth Doctor and Leela stopped him and the migration, which could have caused a temporal paradox with universal ramifications. (AUDIO: The Foe from the Future)