"Madame Kovarian" was a mysterious woman, of whom Amy Pond had recurring visions. She wore an eyepatch or a similar device over her right eye.
The first time Amy saw her was whe she appeared at the little girl's bedroom door at Graystark Hall Children's Home. She appeared through a hatch in the door, which later disappeared. Amy was startled by the woman and asked who she was, but the woman ignored her and said "No, I think she's just dreaming" to someone inside the room. When Amy entered, the room appeared to be empty, with no evidence of the woman or the hatch. (DW: Day of the Moon)
While asleep on a pirate ship, Amy was woken by a noise and saw the woman in a hatch that opened on the hull of the ship. She said, "It's fine. You're doing fine. Just stay calm." This time, she seemed to make eye contact with Amy. (DW: The Curse of the Black Spot)
She is credited as Madame Kovarian in the credits of Day of the Moon and The Curse of the Black Spot