'It'

 'It'  is an animatronic that can be found in the extended demo. The cause of  'it'  is unknown right now, but  'it' was found in a stream.

P.S: This does not have much information on  'it'  due to the fact that would spoil the mystery of  'it' Information here is from things that non extended demo players could have seen without spoiling anything too much.