Board Thread:General Discussion/@comment-25266931-20170112165458/@comment-26397825-20170117140716

The Knight is a Grimm. It's a Possession type Grimm the SDC were experimenting with and her father forced her to defeat in order to secure her place at Beacon. If she failed, she would have to go to Atlas. So even if the shell is one of the standard suits of armour decorating the Schnee Manor, it is possessed by a Grimm and that's why it moves and she can summon it.