Lake 3

Lake 3 was the third incarnation of Lake, a Proto-Time Lord clone of River Song and the leader of a religious cult.

Biography
Now disguised as Mr Quisling, Lake began working with Sharon, taking Quisling's place for three months.

Later he took Lily captive and killed her in front of River Song, realising that she was a proto-Time Lord but not knowing where she came from or who she was. However, Lily didn't regenerate, as she had used up all her allotted regenerations. Furious, River shot Lake dead, only to be shocked when he regenerated into Lily. (AUDIO: The Lady in the Lake)