Tilly was Nancy Norton's maid. She went with Nancy on the expedition to the island of Salutua in 1934. Because the Third Doctor created a time bridge to the island from UNIT in the future, several potential timelines were created. (PROSE: The Eye of the Giant)
Original timeline Edit
She died with the expedition when the volcano on the island erupted after Brokk's ship crashed into it.
Alternate timeline 1 Edit
She was one of the first people who Nancy implanted with Brokk's eyebrain fragments, converting her into a minion. She helped Nancy take over the expedition's crew after leaving the island, then aided in her campaign to control the world.