Siren (The Curse of the Black Spot)

The "Siren" was a virtual doctor from a space ship who accidentally kidnapped pirates from the Fancy.

Biography
The Siren worked on an unnamed spaceship in another dimension. It accidentally became trapped in the same space as the Fancy, with any reflective surfaces acting as portals to the other dimension. The crew was wiped out by a disease from Earth, leaving her with no patients. With nothing to do, she became aware of the Fancy's presence, and sensed any crew member who was wounded in the slightest way (for example, a small cut). She then took tissue samples of the wounded sailor, leaving a black spot, so she could then return and take the sailor to the sick bay to care for. However, even though she could keep her patients alive with life support, she didn't know how to cure their ailments. She continued to do so after the Eleventh Doctor, and Amy Pond arrived, despite their attempts to ward her off.

During a storm, she took Captain Henry Avery's son, Toby. When Rory was knocked off the ship and began to drown, the Doctor exposed a reflective surface so that she could save him. The Doctor, Amy and Captain Avery all allowed themselves to be taken by the Siren to see where they would go. When they found Rory and the crew, Amy showed the Siren her wedding ring, and the Siren gave her consent to care for Rory. Captain Avery knew that his son couldn't be saved, so he took over the space ship with his crew, allowing the Siren to care for them. (DW: The Curse of the Black Spot)

Personality
The Siren appeared to possess limited intelligence, being incapable of communication through any language and being unable to detect the severity of an injury (given that she would take those who had barely more than a simple cut). The Siren refused to let anyone else help her patients unless they were connected in some way, such as marriage in Amy's case. She then required them to "sign a consent form" by placing a hand in a glowing ring that appeared on her palm and confirming that they would take full responsibility for the patient. She was extremely thorough with her job with keeping germs out of sick bay as she nearly burned the Doctor to a crisp for a simple sneeze. (DW: The Curse of the Black Spot)

Abilities
The Siren was capable of taking the image of the injured species; when attempting to treat humans, she looked like a green woman clothed in a gown. When interfered with or faced with contaminated material, she would become red and angry.

When someone was injured, she took a tissue sample from their hand, leaving a black spot, which would be removed as soon as the patient was sent to the sick bay. The Siren's singing acted as an anaesthetic. She used her song to lure individuals to her, although it only affected those from whom she had taken a tissue sample. On touching her, people would be teleported to a sick bay, though if they were under the trance of her song. When Avery, the Doctor and Amy allowed themselves to be taken, they didn't allow her to lull them into a trance as had the others. Her screams were also capable of catapulting people away, as Amy was thrown backwards when she protected from Rory from being taken to sick bay. The Siren could also produce fire to sterilize infected material as evidenced when she nearly roasted the Doctor after a single sneeze. (DW: The Curse of the Black Spot)