Constantine (The Parliament of Rats)

Constantine was the navigator of the Lung of Heaven. She was a time-sensitive, which enabled her to navigate the time fractures on the seas of Lethe. She was very eccentric, and most of the crew avoided her whenever possible.

When the TARDIS crashed into the sea, she led the ship to it, allowing them to rescue the Fifth Doctor and Nyssa. The Lung was attacked and boarded by the Parliament of Rats, a pirate ship, and the crew surrendered to the mutant pirates. Nyssa and Brunner were taken to the Parliament to be sacrificed to the White God. Constantine and the Fifth Doctor rescued them, with Constantine leading them back to the Lung. The Doctor defeated the White God, and the Parliament broke apart, throwing the Doctor into the sea. Constantine rescued him and brought him back to the Lung. Back on board the Lung, the Doctor learned that Constantine had created the White God for her amusement.

The Doctor and Nyssa decided to take Constantine with them if she wished, but before they could ask her, she had vanished. (PROSE: The Parliament of Rats)