Sylva Argento was the Captain of the Proteus.
She was originally an Outsider on Gallifrey, living in the slums of Perdition. When the Civil War began, Argento and other Outsiders were promised a return to Time Lord society and to be given the ability to regenerate if they served in the war. Argento was one of the only Outsiders to actually be awared a regeneration for her actions, receiving it alongside the Horn of Rassilon.
After regenerating from her original male self into a female incarnation after dying at the Devil's Pass, she suffered from post-regenerative mental sickness, needing Gilda to provide her the Elixir of Life to stabilise her mind during the last voyage of the Proteus. She hated many aspects of her new body, including its taste buds and the shape of its mouth.
When the Shimmering Man came aboard the ship, he knew Captain Argento, and told her than on the Isle of the Dead she would see the son of her son. (AUDIO: Morbius [+]Loading...["Morbius (audio story)"])