This set belongs to the Older Madaras Twin and, interestingly enough, can be found near the summoning spot for the Younger Madaras Twin, if players have joined The League and have the Old Hunter Bell.
There are some interesting details surrounding this set:
A capeless version of this set is worn by the Huntsmen who roam the streets below the Abandoned Old Workshop. This is something that is beyond odd, since there is no explanation for them to wear this kind of attire.
Another interesting thing is that the Great Axe-wielding Executioners (found mostly in the Hemwick Charnel Lane by the Cainhurst monument) have a cape design that is exactly the same as the one that the Butcher Garb displays.