User blog comment:Xilinoc/Ch. 568. Hear. Fear. Here 2/@comment-11446176-20140212074009/@comment-5398287-20140213190953

I don't think every Sternritter has it on their body. It's basically the thing that allows them to activate Vollstandig, and it's in different places for different Sternritter (Quilge had a Sanrei Glove, Mask had it on his belt). As just happens to have it on the back of his eyeball because reasons.