Sky Silvestry

Sky Silvestry was a passenger and a businesswoman aboard a tourist craft going around the planet Midnight.

Biography
She was visiting Midnight after the end of her relationship with her female partner. When an unknown force began banging on the side of the vessel, Sky panicked, in the belief that her former lover had returned to get revenge. The force, apparently feeding on her fear, possessed her.

It is not known whether Sky Silvestry's consciousness remained afterward.

While possessed, Sky repeated everything that everybody said, until moving onto the next stage of saying the same thing at exactly the same time. The other passengers became extremely disturbed by this and decided they want Sky thrown off the bus to her death, which the Tenth Doctor objected to. While being spoken to by the Doctor, Sky stole his voice and managed to make him start repeating her, leading the other passengers to believe the lifeform had left Sky and had now possessed the Doctor, but in reality, Sky was still possessed, just progressing.

As Sky convinced the others to chuck the Doctor off the bus, the Hostess realised Sky was still possessed due to her use of the phrases "Allons-y!" and "Molto bene". (The Doctor had spoken these same phrases to the hostess earlier) The Hostess grabbed Sky and pulled her out the door, sacrificing herself and Sky to save the Doctor. (DW: Midnight)