Why is Bazett here?

She doesn't come from this series. I am confused

This image was made before Kagenui and Ononoki had official character designs, so the artist used Bazett and Omokage as substitutes. Same for the Kizumonogatari characters (Meme had a design by this point, but the illustration is captioned "first mental image", so I guess the artist chose to ignore it).

@whoever did translations

The "right foot get" and so on refer to her gradual retrieval of her body parts I think. It makes sense if you read Kizumonogatari.