Question: dark souls 3 where to find vertebra shackle?
Answer: One is gained from defeating mad spirit Holy Knight Hodrick after he invades in the Undead Settlement. ... 
+Item Drop from Carthus Swordsman Skeleton in the Catacombs of Carthus (Very Rare, ~0.8% at 100 Kills with Item Discovery of 100, tested on 100 Kills with 499 Item Discovery).