The Hostess was an unnamed character from Doctor Who who went from being a supporting ally to a selfless hero in the episode "Midnight".
The Hostess worked aboard a space-craft orbiting the mysterious planet Midnight and as such she was responsible for the well-being of the passengers aboard, one of whom would be the Doctor in disguise.
unfortunately for all involved a malevolent and powerful psychic entity known only as the Midnight Entity would manifest and invaded the ship using the body of Sky, the Entity quickly sowed terror and paranoia among the passengers and convinced them that the Doctor was the invader and tried to have the near-insane passengers toss him out into a deadly void.
The Hostess was not entirely convinced but watched on in hapless panic as the passengers began to drag the Doctor towards the ship's exit, yet the malicios Entity made a fatal mistake as it gloated somewhat, using certain phrases unique to the Doctor - which the Hostess caught onto, realizing the Entity was inside Sky the Hostess acted quickly and sacrificed herself as she grabbed Sky and dragged her to the exit, which she promptly opened - sucking both herself and the evil alien into the void, where they presumably died.
After her death the Doctor asked the other passengers what her real name was but they could not answer, she would later be remembered by the Doctor when Davros asked him how many innocents had died because of his actions (though in the Doctor's defence he was in no way responsible for her death, as she had willingly sacrificed herself to stop the Midnight Entity).