The magical beasts of the Potter universe include werewolves, basilisks and now apparently straight-up human flesh eating cannibals?
So where does this particularly dark art fit into the magical world of Harry Potter?
Well, it all comes down to a gap in our understanding of how exactly the very early magical Dark Art of making horcruxes came about.
This is pretty much the formula that is laid out to us:
horcrux = murder + spell + atrocious act
The books are not incredibly elucidating on this rather taboo topic of the wizarding world, but if you want to split your soul and effectively cheat death, it's known that you do need to kill someone with magic, usually the killing curse.
However, as for the atrocious act you then need to commit, it's all up in the air.
So one interesting theory that has surfaced on Reddit by user 'sirlionel13' is that consuming the flesh of your victim after stealing them of their life is an essential part in the horcrux making process.
The purpose of making a horcrux is to become immortal by putting a fragment of your soul into another entity or object. Fragmenting the soul is semi-destructive in the sense that the murderer has to split their soul. Consuming the flesh of your freshly murdered victim is stated by the theory to facilitate this process:
“Voldermort eats people to connect his soul to theirs so their soul rips his out on their way to the afterlife.”
The poster does firmly state that the reason this doesn't apply to Harry is that he is not a true horcrux.
"Harry received a torn off fragment of Tom Riddle's soul only because his soul was so unstable to begin with that the rebounding killing curse ripped a piece of it off, which then possessed the closest living thing to it - Harry."
So, there you go, avid wannabe wizards and witches. Here's one theory of what the atrocious act aspiring horcrux makers have to commit. Let's remind ourselves of that excellent scene from The Half-Blood Prince when Tom Riddle asks Slughorn about that "little bit of rare magic."