Moloch (Protect and Survive)

Moloch was the oldest and most powerful of the Great Old Ones, who according to legend was born in "the fires of creation", and was the god of chaos.

He had agents to do his work for him and they took the form of several real life humans including Albert and Peggy Marsden, who were instructed to destroy the Earth. But these two were trapped inside a pocket dimension created by the Seventh Doctor. The dimensional prison takes the form of a ten-day time loop and only exists as long as the Great Old Ones are trapped within it, preventing Moloch from freeing them. The Doctor meant them to understand what it is to live and die as mortal humans, and promised to release them once they could do this; they had been trapped for several hundred years in their efforts, however.

In world events created by Moloch, which was presumably erased after the Doctor actions, the Berlin wall did not fall and Communism remained. Popular risings in the Eastern bloc lead to the Soviet Union's General Secretary Vladimir Kryuchkov ordering tanks, and troops to fire on the protesters. When American bases in West Berlin come under Soviet control the United States issues an ultimatum and, when this is ignored, they bombed a town on the border of West Germany, escalating the likelihood of nuclear war, which in the Doctor's trap came to pass. (AUDIO: Protect and Survive)