Brainstorm

A vampire is the undead body of a living person who returns from the grave to feed on the blood of the living.

Are there monsters who feed on other parts of the body?

>Skin
>Muscles
>Hair
>Nails
>Bones
>Lungs
>Bladders
>Hearts
>Eyes
>Etc

What are they like?

A ghoul.

They do all of the above.

Could have something along the same vein as a mermaid that needs to suck the lungs out of people in order to breathe on land?

Succubi.

IIRC bone marrow is a popular choice for certain, more "bestial", varieties of undead. It has a nice thematic parallel: Marrow is the raw, unrefined source of blood, and as such is consumed by the relatively more unrefined undead.

The problem with a lot of these is that they're kinda real specific. Like, brain and blood are obviously generally important to keeping you alive. Your liver? Yeah it's important but I dunno what it does. It ain't gonna be as scary.

I like the idea of original Mummy movie, where Imhotep went around stealing the organs of people to reconstruct himself.

I may lift that for a campaign villain actually

The Scavengers
>Skin
The fluttering one. It wafts on the wind until it scents death. It sinks like a rock and slips into the grave. Strips the skin from the muscle
>Muscles
The brutal one. An observer can tell it has been near when a grave is ripped from the earth. The corpse will have no muscle.
>Hair
The irritating one. None have seen it, for when it is near the eyes will water and the nose will itch. The throat will hurt and the skin will tingle. Only when observers have been warned away does it feed, leaving the corpse stripped of all hair.
>Nails
The clicking one. Brother of the irritating one and enemy of the crunching one. It strides across the graveyard, clicking in order to find its way through the dark. When it comes upon a grave, it plucks the nails from the corpse with a thin beak.
>Bones
The crunching one. A destructive thing, it loves to test its jaws. It smashes gravestones to gravel and trees into splinters. Any corpse it finds is split in two and emptied of bone.
>Lungs
The groaning one. It drifts into graveyards under the cover of darkness. It is never quiet, howling and whistling and shrieking and moaning. It forms a seal on the mouth of the corpse, and sucks out the lungs.
>Bladders
The soggy one. Erupting from the ground during heavy rain, it is not graceful. It drags itself along with an oversized arm, the rest of its body flowing limply behind. It simply tears what it needs from a corpse.
>Hearts
The ceremonial one. Nobody knows where it comes from, and it simply appears on a chosen grave. Its long fingers scratch symbols into the dirt as it sings alien hymns for hours on end. When it leaves, the heart leaves with it.
>Eyes
The peeping one. It knows not when one is near death, but is determined to be there when they are. It will watch the victim from hidden spaces and secret places for years on end. The moment they die, it will take their eyes regardless of who's watching.

Well, undead are magic, so you can extrapolate like a motherfucker and get thematic. The scary part doesn't need to come from what and how they take, but what they do with it.

So, take the liver. It's purpose is to filter out toxins, poisons, and all kinds of bad stuff. So, the creature that consumes your liver loves that shit. It is poison personified. It's mere touch may render you sick for days. A bite is guaranteed to fester and bring certain death. It is a being of calculated malice, seeking out rivers, springs, and wells to poison, so it gets more corpses to pilfer delicious livers from. And the more it consumes, the deadlier it becomes...

There are monsters that eat hearts and livers; I know for a fact that the Kumiho does. I don't know about undeads, though.