Board Thread:General Discussion/@comment-27234079-20190901125053/@comment-29684190-20190902132846

yeah. she stole amber's powers using a grimm bug that then seemingly went inside her to bond maiden magic to her. And when Ruby blased her silver eyes the grimm bug blow up or something hurting cinder. Someone made a detailed analysis how cinder was hit from one side by the blast and the beetle would try to escape through her body through the other side so that's why she took so much damage and an arm.

Andway, from volume 4 onward she had her left arm replaced by a grimm one. It's the same model as a geist arm, but there are questions if it's actually a geist arm or not. Like, she fell down and clutched her arm when ruby used a silver blast in Haven.