A Good Man Goes to War - S6-E8
Revealing mistake: Several of the hallways in Demon's Run, particularly the one where Madame Kovarian has the baby brought to her and the one the Doctor's standing in when he realises where Amy and Rory's baby was conceived, are the repainted sets of the TARDIS hallways from "The Doctor's Wife", three episodes before.
Chosen answer: No, no information is avalible for the identity of the entity.
Repo_Man