Deep Breath - S8-E1
Revealing mistake: After the clockwork droids shut down, when the ones in the restaurant basement start falling over, the extended blade of one of the toppling droids flops about like rubber. (01:08:15)
Revealing mistake: When the old man is stabbed, the sword is retracted and we can see there is no blood visible on the sword. This is visible even before the blood is wiped off. (00:06:55)
Revealing mistake: When Robin Hood comes up behind the Doctor to push him into the water, it's obviously a stunt double with a bad wig.
Revealing mistake: During the scene at the beginning where people are taking pictures of themselves with the Cybermen, there are a few moments where the Cybermen's armour is revealed to be rubber when people touch it. (00:02:45)
Revealing mistake: During the sequence where the Cyber-clouds covering Earth are burned away, there is a shot showing the clouds burning over the Sydney Opera House. The shot is, very obviously, a still image to which CGI of the burning sky has been added, with extremely unconvincing results. (00:47:37)
Chosen answer: No, no information is avalible for the identity of the entity.
Repo_Man