Harry Potter and the Deathly Hallows Part 2 Trailer?

in the trailer of harry potter and the deathly hallows part 2 we see a single black knight (suit of armour) drop from the ceiling in hogwarts and then few frames later we see a whole army of them what are they doing and whose side are they on



(if your not sure which trailer this one: http://www.youtube.com/watch?v=mObK5XD8udk)Harry Potter and the Deathly Hallows Part 2 Trailer?
The knights are actually the statues of knights that are placed at Hogwarts.

Mcgonagall bewitches them and asks them to do their duty by protecting Hogwarts against the Death Eaters :)Harry Potter and the Deathly Hallows Part 2 Trailer?
The Order of the Phoenix's side. Remember the suits of armor in Hogwarts? They start fighting against the Death Eaters.

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