User blog comment:Xilinoc/Ch. 542 - THE BLADE IS ME/@comment-11051098-20130619142823/@comment-11051098-20130620181434

I went back to the chapter it happened in, and it seems I've missed that. It does seem like he appears in front of Shaz Domino and kills him. So by the count I've been able to make, 8 Stern Ritters have been killed.

So if the theory of a total of 27 Stern Ritters resembling the alphabet should be true, including double Y in the Lloyd twins, there's from my count at least 19 remaining.

And if those 18 ones Yhwach talked to in the last page are Stern Ritters, there's at least 18 + the surviving ones from the first battle, Bambietta, Buzzbee, 2 unnamed ones (the guy with the glasses who injured Kyôraku and the unknown guy who faced Hitsugaya and Rangiku), and Haschwalth.